Class DateUtil

Provides a comprehensive set of static utility methods for working with DateTime values, including culture-aware formatting and parsing, date arithmetic, boundary calculations (start/end of day, week, month, year), calendar queries, human-readable relative descriptions, Unix timestamp conversions, and age calculations.

Inheritance
object
DateUtil
Inherited Members
Namespace: Scylla.Core.Util
Assembly: ScyllaCore.dll
Syntax
public static class DateUtil
Remarks

All formatting and parsing operations use the culture set via the Culture property, which defaults to InvariantCulture for consistent, locale-independent results. Change Culture once at application startup if you need locale-specific output (e.g., locale date separators, month names).

ISO 8601 methods (ToISO8601(DateTime, bool), ToISO8601UTC(DateTime), ParseISO8601(string)) always use InvariantCulture regardless of the Culture setting, ensuring portable interchange formats.

Predefined format constants such as FORMAT_ISO_DATE, FORMAT_HH_MM_SS, and FORMAT_SORTABLE can be passed directly to any method that accepts a format parameter.

Fields

FORMAT_DD_MM_YYYY

Day/Month/Year format (e.g., "15/01/2026").

Declaration
public const string FORMAT_DD_MM_YYYY = "dd/MM/yyyy"
Field Value
Type Description
string

FORMAT_FULL_LONG

Full date/time long pattern.

Declaration
public const string FORMAT_FULL_LONG = "F"
Field Value
Type Description
string

FORMAT_FULL_SHORT

Full date/time short pattern.

Declaration
public const string FORMAT_FULL_SHORT = "f"
Field Value
Type Description
string

FORMAT_GENERAL_LONG

General date/time long pattern.

Declaration
public const string FORMAT_GENERAL_LONG = "G"
Field Value
Type Description
string

FORMAT_GENERAL_SHORT

General date/time short pattern.

Declaration
public const string FORMAT_GENERAL_SHORT = "g"
Field Value
Type Description
string

FORMAT_HH_MM

Time with hours and minutes (e.g., "14:30").

Declaration
public const string FORMAT_HH_MM = "HH:mm"
Field Value
Type Description
string

FORMAT_HH_MM_SS

Time with hours, minutes, seconds (e.g., "14:30:00").

Declaration
public const string FORMAT_HH_MM_SS = "HH:mm:ss"
Field Value
Type Description
string

FORMAT_ISO_8601_UTC

ISO 8601 UTC format (e.g., "2026-01-15T14:30:00Z").

Declaration
public const string FORMAT_ISO_8601_UTC = "yyyy-MM-ddTHH:mm:ssZ"
Field Value
Type Description
string

FORMAT_ISO_DATE

ISO 8601 date format (e.g., "2026-01-15").

Declaration
public const string FORMAT_ISO_DATE = "yyyy-MM-dd"
Field Value
Type Description
string

FORMAT_ISO_DATETIME

ISO 8601 date/time format (e.g., "2026-01-15T14:30:00").

Declaration
public const string FORMAT_ISO_DATETIME = "yyyy-MM-ddTHH:mm:ss"
Field Value
Type Description
string

FORMAT_LONG_DATE

Long date pattern (e.g., "Wednesday, January 15, 2026").

Declaration
public const string FORMAT_LONG_DATE = "D"
Field Value
Type Description
string

FORMAT_LONG_TIME

Long time pattern (e.g., "2:30:00 PM").

Declaration
public const string FORMAT_LONG_TIME = "T"
Field Value
Type Description
string

FORMAT_MM_DD_YYYY

Month/Day/Year format (e.g., "01/15/2026").

Declaration
public const string FORMAT_MM_DD_YYYY = "MM/dd/yyyy"
Field Value
Type Description
string

FORMAT_SHORT_DATE

Short date pattern (e.g., "1/15/2026").

Declaration
public const string FORMAT_SHORT_DATE = "d"
Field Value
Type Description
string

FORMAT_SHORT_TIME

Short time pattern (e.g., "2:30 PM").

Declaration
public const string FORMAT_SHORT_TIME = "t"
Field Value
Type Description
string

FORMAT_SORTABLE

Sortable date/time pattern.

Declaration
public const string FORMAT_SORTABLE = "s"
Field Value
Type Description
string

FORMAT_UNIVERSAL

Universal sortable date/time pattern.

Declaration
public const string FORMAT_UNIVERSAL = "u"
Field Value
Type Description
string

FORMAT_YYYY_MM_DD

Year/Month/Day format (e.g., "2026/01/15").

Declaration
public const string FORMAT_YYYY_MM_DD = "yyyy/MM/dd"
Field Value
Type Description
string

FORMAT_YYYY_MM_DD_DASH

Year-Month-Day with dashes (e.g., "2026-01-15").

Declaration
public const string FORMAT_YYYY_MM_DD_DASH = "yyyy-MM-dd"
Field Value
Type Description
string

UNIX_EPOCH

Unix epoch start date (January 1, 1970 00:00:00 UTC).

Declaration
public static readonly DateTime UNIX_EPOCH
Field Value
Type Description
DateTime

Properties

Culture

Gets or sets the culture used for all date formatting and parsing operations performed by this utility class. Defaults to InvariantCulture to produce locale-independent output. Setting this to a specific culture (e.g., CultureInfo.GetCultureInfo("en-US")) affects month names, date separators, and AM/PM designators in format strings that include those components.

Declaration
public static CultureInfo Culture { get; set; }
Property Value
Type Description
CultureInfo

The CultureInfo used for formatting and parsing. Never null.
Remarks

Assigning null resets the value to InvariantCulture rather than throwing an exception. ISO 8601 methods always use InvariantCulture regardless of this property.

Methods

AddDays(DateTime, int)

Returns a new DateTime that adds the specified number of whole days to dateTime. Delegates to AddDays(double).

Declaration
public static DateTime AddDays(DateTime dateTime, int days)
Parameters
Type Name Description
DateTime dateTime

The base date and time to add to.
int days

The number of days to add. Pass a negative value to subtract days. Fractional values are not accepted because the parameter is typed as int.
Returns
Type Description
DateTime

A new DateTime offset from dateTime by days days.

AddMonths(DateTime, int)

Returns a new DateTime that adds the specified number of whole months to dateTime, using calendar-aware arithmetic that accounts for varying month lengths. For example, adding one month to January 31 yields February 28/29. Delegates to AddMonths(int).

Declaration
public static DateTime AddMonths(DateTime dateTime, int months)
Parameters
Type Name Description
DateTime dateTime

The base date and time to add to.
int months

The number of months to add. Pass a negative value to subtract months.
Returns
Type Description
DateTime

A new DateTime offset by months months.

AddYears(DateTime, int)

Returns a new DateTime that adds the specified number of whole years to dateTime. Handles leap-year edge cases (e.g., Feb 29 becomes Feb 28 in a non-leap target year). Delegates to AddYears(int).

Declaration
public static DateTime AddYears(DateTime dateTime, int years)
Parameters
Type Name Description
DateTime dateTime

The base date and time to add to.
int years

The number of years to add. Pass a negative value to subtract years.
Returns
Type Description
DateTime

A new DateTime offset by years years.

Format(DateTime, string)

Formats the specified dateTime value using the given format string and the active Culture. Defaults to FORMAT_GENERAL_LONG when no format is specified.

Declaration
public static string Format(DateTime dateTime, string format = "G")
Parameters
Type Name Description
DateTime dateTime

The DateTime value to format.
string format

A standard or custom .NET date-time format pattern. Defaults to FORMAT_GENERAL_LONG. Must not be null or empty.
Returns
Type Description
string

A string representation of dateTime using the specified format and culture.
Exceptions
Type Condition
ArgumentNullException

Thrown when format is null or empty.

FromUnixTimestamp(long)

Converts a Unix timestamp (seconds since UNIX_EPOCH) to a DateTime in UTC. The result always has Utc because UNIX_EPOCH is a UTC value.

Declaration
public static DateTime FromUnixTimestamp(long timestamp)
Parameters
Type Name Description
long timestamp

Seconds elapsed since 1970-01-01 00:00:00 UTC. May be negative for pre-epoch values.
Returns
Type Description
DateTime

A DateTime with Utc corresponding to timestamp seconds after the epoch.

FromUnixTimestampMilliseconds(long)

Converts a Unix timestamp in milliseconds to a DateTime in UTC. Counterpart to ToUnixTimestampMilliseconds(DateTime). The result always has Utc.

Declaration
public static DateTime FromUnixTimestampMilliseconds(long timestampMilliseconds)
Parameters
Type Name Description
long timestampMilliseconds

Milliseconds elapsed since 1970-01-01 00:00:00 UTC. May be negative for pre-epoch values.
Returns
Type Description
DateTime

A DateTime with Utc corresponding to timestampMilliseconds milliseconds after the epoch.

GetAge(DateTime)

Calculates the age in complete years from birthDate to today's date (Today). The birthday is considered to have occurred if both the month and the day-of-month of the current date are greater than or equal to the corresponding values of birthDate.

Declaration
public static int GetAge(DateTime birthDate)
Parameters
Type Name Description
DateTime birthDate

The date of birth. Only the date component is used; the time is ignored.
Returns
Type Description
int

The number of complete years elapsed since birthDate. Returns a negative value if birthDate is in the future.

GetAge(DateTime, DateTime)

Calculates the age in complete years from birthDate to referenceDate. Correctly accounts for whether the birthday has passed in the reference year by comparing month and day components.

Declaration
public static int GetAge(DateTime birthDate, DateTime referenceDate)
Parameters
Type Name Description
DateTime birthDate

The date of birth. Only the date component is used.
DateTime referenceDate

The date at which to calculate the age. Typically today, but can be any past or future date to compute a hypothetical age.
Returns
Type Description
int

The number of complete years elapsed from birthDate to referenceDate. Negative if referenceDate precedes birthDate.

GetDayOfYear(DateTime)

Returns the one-based ordinal day number within the year (1-366) for the given dateTime. Equivalent to dateTime.DayOfYear.

Declaration
public static int GetDayOfYear(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

The DateTime to query.
Returns
Type Description
int

An integer in the range 1-366 representing the day within the year.

GetDaysBetween(DateTime, DateTime)

Returns the number of whole calendar days between two dates, ignoring the time-of-day component. The result is computed as (end.Date - start.Date).TotalDays and can be negative when end precedes start.

Declaration
public static int GetDaysBetween(DateTime start, DateTime end)
Parameters
Type Name Description
DateTime start

The earlier (or reference) date.
DateTime end

The later (or target) date.
Returns
Type Description
int

The signed number of whole days from start to end. Negative if end is before start.

GetDaysInMonth(DateTime)

Returns the number of days in the month of the given dateTime, taking leap years into account for February. Delegates to DaysInMonth(int, int).

Declaration
public static int GetDaysInMonth(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

The DateTime whose month is queried.
Returns
Type Description
int

28, 29, 30, or 31 depending on the month and year.

GetDaysInMonth(int, int)

Returns the number of days in month for the given year, taking leap years into account. Delegates to DaysInMonth(int, int).

Declaration
public static int GetDaysInMonth(int year, int month)
Parameters
Type Name Description
int year

The Gregorian year.
int month

The month number in the range 1-12.
Returns
Type Description
int

28, 29, 30, or 31 depending on the month and year.

GetDaysInYear(DateTime)

Returns the total number of days in the year of dateTime. Returns 366 for leap years and 365 for non-leap years.

Declaration
public static int GetDaysInYear(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

The DateTime whose year is queried.
Returns
Type Description
int

365 or 366.

GetDaysInYear(int)

Returns the total number of days in the specified year. Returns 366 for leap years and 365 for non-leap years.

Declaration
public static int GetDaysInYear(int year)
Parameters
Type Name Description
int year

The Gregorian year to query.
Returns
Type Description
int

365 or 366.

GetEndOfDay(DateTime)

Returns the last representable tick of the day containing dateTime, computed as dateTime.Date.AddDays(1).AddTicks(-1) (i.e., 23:59:59.9999999).

Declaration
public static DateTime GetEndOfDay(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

Any DateTime value within the target day.
Returns
Type Description
DateTime

A DateTime representing one tick before the start of the following day.

GetEndOfMonth(DateTime)

Returns the last tick of the final day of the month containing dateTime. Computed by advancing to the start of the next month and subtracting one tick.

Declaration
public static DateTime GetEndOfMonth(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

Any DateTime value within the target month.
Returns
Type Description
DateTime

A DateTime representing the last representable moment of the month.

GetEndOfWeek(DateTime, DayOfWeek)

Returns the last tick of the final day of the calendar week that contains dateTime, consistent with the startOfWeek convention. Computed as GetStartOfWeek(dateTime, startOfWeek).AddDays(7).AddTicks(-1).

Declaration
public static DateTime GetEndOfWeek(DateTime dateTime, DayOfWeek startOfWeek = DayOfWeek.Sunday)
Parameters
Type Name Description
DateTime dateTime

Any DateTime value within the target week.
DayOfWeek startOfWeek

The day of the week considered the first day. Defaults to Sunday.
Returns
Type Description
DateTime

A DateTime representing the last tick of the last day of the week.

GetEndOfYear(DateTime)

Returns the last representable tick of December 31 of the year containing dateTime. Computed by advancing to January 1 of the next year and subtracting one tick.

Declaration
public static DateTime GetEndOfYear(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

Any DateTime value within the target year.
Returns
Type Description
DateTime

A DateTime representing the last tick of December 31 of the same year.

GetMonthsBetween(DateTime, DateTime)

Returns the number of complete calendar months between two dates, calculated as (end.Year - start.Year) * 12 + end.Month - start.Month. The result does not account for the day-of-month component, so a start of Jan 31 and an end of Feb 1 returns 1. Use GetDaysBetween(DateTime, DateTime) for day-accurate intervals.

Declaration
public static int GetMonthsBetween(DateTime start, DateTime end)
Parameters
Type Name Description
DateTime start

The reference date.
DateTime end

The target date. Can precede start, yielding a negative result.
Returns
Type Description
int

The signed approximate number of months from start to end.

GetQuarter(DateTime)

Returns the fiscal quarter (1-4) for the given dateTime, based on the Gregorian calendar. Q1 = Jan-Mar, Q2 = Apr-Jun, Q3 = Jul-Sep, Q4 = Oct-Dec. Computed as (month - 1) / 3 + 1.

Declaration
public static int GetQuarter(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

The DateTime to query.
Returns
Type Description
int

An integer in the range 1-4 representing the calendar quarter.

GetRelativeDescription(DateTime)

Returns a plain-English sentence describing how dateTime relates to the current local time (Now). The description is always in English regardless of the active Culture setting.

Declaration
public static string GetRelativeDescription(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

The DateTime value to describe relative to now.
Returns
Type Description
string

A human-readable phrase such as "just now", "3 minutes ago", "in 2 hours", "1 day ago", or "in 3 years". See GetRelativeDescription(DateTime, DateTime) for the full set of thresholds.

GetRelativeDescription(DateTime, DateTime)

Returns a plain-English sentence describing how dateTime relates to referenceTime. Output is in English regardless of Culture. The description uses the following threshold ladder:

  • Less than 60 seconds: "just now"
  • Less than 60 minutes: "N minute(s) ago" / "in N minute(s)"
  • Less than 24 hours: "N hour(s) ago" / "in N hour(s)"
  • Less than 7 days: "N day(s) ago" / "in N day(s)"
  • Less than 30 days: "N week(s) ago" / "in N week(s)"
  • Less than 365 days: "N month(s) ago" / "in N month(s)"
  • 365+ days: "N year(s) ago" / "in N year(s)"
Declaration
public static string GetRelativeDescription(DateTime dateTime, DateTime referenceTime)
Parameters
Type Name Description
DateTime dateTime

The DateTime to describe.
DateTime referenceTime

The reference point to measure from (e.g., Now for real-time descriptions).
Returns
Type Description
string

A human-readable phrase describing the temporal distance and direction.

GetStartOfDay(DateTime)

Returns the midnight boundary of the day containing dateTime, equivalent to dateTime.Date. The DateTimeKind of the original value is preserved.

Declaration
public static DateTime GetStartOfDay(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

Any DateTime value within the target day.
Returns
Type Description
DateTime

A DateTime with the same year, month, and day as dateTime and a time component of 00:00:00.000.

GetStartOfMonth(DateTime)

Returns midnight on the first day of the month containing dateTime. The DateTimeKind of the original value is preserved.

Declaration
public static DateTime GetStartOfMonth(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

Any DateTime value within the target month.
Returns
Type Description
DateTime

A DateTime at 00:00:00 on day 1 of the same month and year.

GetStartOfWeek(DateTime, DayOfWeek)

Returns the midnight of the first day of the calendar week that contains dateTime, using startOfWeek to define which day opens the week. Defaults to Sunday, consistent with US conventions; pass Monday for ISO 8601 week boundaries.

Declaration
public static DateTime GetStartOfWeek(DateTime dateTime, DayOfWeek startOfWeek = DayOfWeek.Sunday)
Parameters
Type Name Description
DateTime dateTime

Any DateTime value within the target week.
DayOfWeek startOfWeek

The day of the week considered the first day. Defaults to Sunday.
Returns
Type Description
DateTime

A DateTime at midnight (00:00:00) on the opening day of the week.

GetStartOfYear(DateTime)

Returns midnight on January 1 of the year containing dateTime. The DateTimeKind of the original value is preserved.

Declaration
public static DateTime GetStartOfYear(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

Any DateTime value within the target year.
Returns
Type Description
DateTime

A DateTime at 00:00:00 on January 1 of the same year.

GetWeekOfYear(DateTime, CalendarWeekRule, DayOfWeek)

Returns the week number of the year for dateTime according to the specified rule and firstDayOfWeek. Uses the calendar of the active Culture. The range is 1-53 depending on the rule and year.

Declaration
public static int GetWeekOfYear(DateTime dateTime, CalendarWeekRule rule = CalendarWeekRule.FirstDay, DayOfWeek firstDayOfWeek = DayOfWeek.Sunday)
Parameters
Type Name Description
DateTime dateTime

The DateTime to query.
CalendarWeekRule rule

Determines how the first week of the year is identified. Defaults to FirstDay (week 1 = any week containing Jan 1).
DayOfWeek firstDayOfWeek

The day considered the start of the week. Defaults to Sunday.
Returns
Type Description
int

The week-of-year number (1-53).

GetYearsBetween(DateTime, DateTime)

Returns the number of complete calendar years elapsed from start to end, accounting for whether the anniversary month and day have been reached in the ending year. The result is always a whole number and can be negative.

Declaration
public static int GetYearsBetween(DateTime start, DateTime end)
Parameters
Type Name Description
DateTime start

The reference date (e.g., a birth date).
DateTime end

The target date. Can precede start, yielding a negative result.
Returns
Type Description
int

The signed number of complete years from start to end.

IsFuture(DateTime)

Determines whether the specified DateTime is in the future.

Declaration
public static bool IsFuture(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

The DateTime to check.
Returns
Type Description
bool

True if the date is in the future; otherwise, false.

IsLeapYear(DateTime)

Determines whether the year of the specified DateTime is a leap year.

Declaration
public static bool IsLeapYear(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

The DateTime to check.
Returns
Type Description
bool

True if the year is a leap year; otherwise, false.

IsLeapYear(int)

Determines whether the specified year is a leap year.

Declaration
public static bool IsLeapYear(int year)
Parameters
Type Name Description
int year

The year to check.
Returns
Type Description
bool

True if the year is a leap year; otherwise, false.

IsPast(DateTime)

Determines whether the specified DateTime is in the past.

Declaration
public static bool IsPast(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

The DateTime to check.
Returns
Type Description
bool

True if the date is in the past; otherwise, false.

IsSameDay(DateTime, DateTime)

Determines whether two DateTimes are on the same day.

Declaration
public static bool IsSameDay(DateTime date1, DateTime date2)
Parameters
Type Name Description
DateTime date1

The first DateTime.
DateTime date2

The second DateTime.
Returns
Type Description
bool

True if both dates are on the same day; otherwise, false.

IsSameMonth(DateTime, DateTime)

Determines whether two DateTimes are in the same month and year.

Declaration
public static bool IsSameMonth(DateTime date1, DateTime date2)
Parameters
Type Name Description
DateTime date1

The first DateTime.
DateTime date2

The second DateTime.
Returns
Type Description
bool

True if both dates are in the same month; otherwise, false.

IsSameYear(DateTime, DateTime)

Determines whether two DateTimes are in the same year.

Declaration
public static bool IsSameYear(DateTime date1, DateTime date2)
Parameters
Type Name Description
DateTime date1

The first DateTime.
DateTime date2

The second DateTime.
Returns
Type Description
bool

True if both dates are in the same year; otherwise, false.

IsToday(DateTime)

Determines whether the specified DateTime is today.

Declaration
public static bool IsToday(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

The DateTime to check.
Returns
Type Description
bool

True if the date is today; otherwise, false.

IsWeekday(DateTime)

Determines whether the specified date falls on a weekday (Monday through Friday).

Declaration
public static bool IsWeekday(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

The DateTime to check.
Returns
Type Description
bool

True if the date is a weekday; otherwise, false.

IsWeekend(DateTime)

Determines whether the specified date falls on a weekend (Saturday or Sunday).

Declaration
public static bool IsWeekend(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

The DateTime to check.
Returns
Type Description
bool

True if the date is a weekend; otherwise, false.

NowString(string)

Returns the current local date and time formatted with the specified format string, defaulting to FORMAT_GENERAL_LONG (e.g., "1/15/2026 2:30:00 PM"). Unlike TodayString(), this includes the time-of-day component.

Declaration
public static string NowString(string format = "G")
Parameters
Type Name Description
string format

A standard or custom .NET date-time format pattern. Defaults to FORMAT_GENERAL_LONG. Must not be null or empty.
Returns
Type Description
string

The current date and time formatted according to format and the active Culture.
Exceptions
Type Condition
ArgumentNullException

Thrown when format is null or empty.

Parse(string, string)

Parses dateString using the specified format and the active Culture. Uses ParseExact(string, string, IFormatProvider, DateTimeStyles) with None, so the string must match the format exactly. Defaults to FORMAT_ISO_DATE when no format is given.

Declaration
public static DateTime Parse(string dateString, string format = "yyyy-MM-dd")
Parameters
Type Name Description
string dateString

The date string to parse. Must not be null or empty.
string format

The exact format pattern the string is expected to match. Defaults to FORMAT_ISO_DATE ("yyyy-MM-dd"). Must not be null or empty.
Returns
Type Description
DateTime

The DateTime value parsed from dateString.
Exceptions
Type Condition
ArgumentNullException

Thrown when dateString or format is null or empty.
FormatException

Thrown when dateString does not match format. Use TryParse(string, out DateTime, string) for non-throwing parsing.

ParseISO8601(string)

Parses an ISO 8601 formatted string using Parse(string, IFormatProvider, DateTimeStyles) with RoundtripKind and InvariantCulture. Accepts the full range of ISO 8601 variants including date-only ("2026-01-15"), date-time ("2026-01-15T14:30:00"), and UTC-offset forms ("2026-01-15T14:30:00Z"). The RoundtripKind style preserves DateTimeKind information embedded in the string.

Declaration
public static DateTime ParseISO8601(string isoString)
Parameters
Type Name Description
string isoString

An ISO 8601 formatted date or date-time string. Must not be null or empty.
Returns
Type Description
DateTime

The DateTime value represented by isoString.
Exceptions
Type Condition
ArgumentNullException

Thrown when isoString is null or empty.
FormatException

Thrown when isoString is not a valid ISO 8601 string.

ToISO8601(DateTime, bool)

Formats the specified dateTime as an ISO 8601 string using InvariantCulture (unaffected by Culture). When includeTime is true, uses FORMAT_ISO_DATETIME (e.g., "2026-01-15T14:30:00"). When false, uses FORMAT_ISO_DATE (e.g., "2026-01-15").

Declaration
public static string ToISO8601(DateTime dateTime, bool includeTime = true)
Parameters
Type Name Description
DateTime dateTime

The DateTime value to convert. No UTC conversion is applied; the value is formatted as-is.
bool includeTime

true to include the time-of-day component; false for date-only output. Defaults to true.
Returns
Type Description
string

An ISO 8601 formatted string representation of dateTime.

ToISO8601UTC(DateTime)

Converts the specified dateTime to UTC and formats it as an ISO 8601 UTC string using the FORMAT_ISO_8601_UTC pattern (e.g., "2026-01-15T14:30:00Z"). Always uses InvariantCulture.

Declaration
public static string ToISO8601UTC(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

The DateTime value to convert. If the value's Kind is Local or Unspecified, it is first converted to UTC via ToUniversalTime().
Returns
Type Description
string

An ISO 8601 UTC-formatted string ending with the Z suffix.

ToUnixTimestamp(DateTime)

Converts dateTime to a Unix timestamp - the number of whole seconds elapsed since the Unix epoch (UNIX_EPOCH, 1970-01-01 00:00:00 UTC). The input is first converted to UTC via ToUniversalTime().

Declaration
public static long ToUnixTimestamp(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

The date and time to convert. If Kind is Local or Unspecified, it is converted to UTC before the calculation.
Returns
Type Description
long

A signed 64-bit integer representing seconds since the Unix epoch. Negative for dates before 1970-01-01 UTC.

ToUnixTimestampMilliseconds(DateTime)

Converts dateTime to a Unix timestamp in milliseconds - the number of whole milliseconds elapsed since UNIX_EPOCH (1970-01-01 00:00:00 UTC). The input is first converted to UTC. Use this for JavaScript Date.getTime() interoperability or when second-precision is insufficient.

Declaration
public static long ToUnixTimestampMilliseconds(DateTime dateTime)
Parameters
Type Name Description
DateTime dateTime

The date and time to convert. Converted to UTC before calculation.
Returns
Type Description
long

A signed 64-bit integer representing milliseconds since the Unix epoch.

TodayString()

Returns the current local date formatted with the FORMAT_SHORT_DATE pattern (e.g., "1/15/2026" with InvariantCulture). The output is culture-sensitive if Culture has been changed from its default.

Declaration
public static string TodayString()
Returns
Type Description
string

The current date as a short-date string using the active Culture.

TodayString(string)

Returns the current local date formatted with the specified format string. Use one of the predefined FORMAT_* constants or a custom .NET date-format pattern.

Declaration
public static string TodayString(string format)
Parameters
Type Name Description
string format

A standard or custom .NET date-format pattern (e.g., FORMAT_ISO_DATE, FORMAT_LONG_DATE). Must not be null or empty.
Returns
Type Description
string

The current date formatted according to format and the active Culture.
Exceptions
Type Condition
ArgumentNullException

Thrown when format is null or empty.

TryParse(string, out DateTime, string)

Attempts to parse dateString using the specified format and the active Culture, without throwing on failure. Returns false and sets result to MinValue when the input is null, empty, or does not match the format.

Declaration
public static bool TryParse(string dateString, out DateTime result, string format = "yyyy-MM-dd")
Parameters
Type Name Description
string dateString

The date string to parse. Returns false if null or empty.
DateTime result

When this method returns true, the parsed DateTime value. When this method returns false, MinValue.
string format

The exact format pattern the string must match. Defaults to FORMAT_ISO_DATE. Returns false if null or empty.
Returns
Type Description
bool

true if parsing succeeded; otherwise false.

TryParseAny(string, out DateTime)

Attempts to parse dateString against multiple commonly used date formats in a single call. Tries formats in the following order: FORMAT_ISO_DATE, FORMAT_ISO_DATETIME, FORMAT_DD_MM_YYYY, FORMAT_MM_DD_YYYY, FORMAT_YYYY_MM_DD, FORMAT_YYYY_MM_DD_DASH, and FORMAT_SORTABLE. Returns false and sets result to MinValue when none of the formats match or the input is null or empty.

Declaration
public static bool TryParseAny(string dateString, out DateTime result)
Parameters
Type Name Description
string dateString

The date string to attempt parsing. Returns false if null or empty.
DateTime result

When this method returns true, the parsed DateTime value. When this method returns false, MinValue.
Returns
Type Description
bool

true if any format successfully parsed dateString; otherwise false.