DateUtils unit

Date/Time manipulation routines.

DateUtils contains a large number of date/time manipulation routines, all based on the TDateTime type. There are routines for date/time math, for comparing dates and times, for composing dates and decomposing dates in their constituent parts.

Classes and records

`EDateTimeException`	class
`ELocalTimeInvalid`	class
`TDateTimeHelper`	helper
`TTimeZone`	class

Procedures and functions

`CompareDate`	function	Compare 2 dates, disregarding the time of day.
`CompareDateTime`	function	Compare 2 dates, taking into account the time of day.
`CompareTime`	function	Compares two times of the day, disregarding the date part.
`DateInRange`	function	Checks whether a date value is in a given rang.
`DateOf`	function	Extract the date part from a TDateTime indication.
`DateTimeInRange`	function	Checks whether a date/time value is in a given range.
`DateTimeToDosDateTime`	function	Convert TDateTime format to DOS date/time format.
`DateTimeToJulianDate`	function	Converts a TDateTime value to a Julian date representation.
`DateTimeToMac`	function	Convert a TDateTime timestamp to a Mac timestamp.
`DateTimeToModifiedJulianDate`	function	Convert a TDateTime value to a modified Julian date representation.
`DateTimeToUnix`	function	Convert a TDateTime value to Unix epoch time.
`DateToISO8601`	function	Converts a TDateTime value to ISO 8601 date/time format.
`DayOf`	function	Extract the day (of month) part from a TDateTime value.
`DayOfTheMonth`	function	Extract the day (of month) part of a TDateTime value.
`DayOfTheWeek`	function	Extracts the day of the week from a TDateTime value.
`DayOfTheYear`	function	Extracts the day of the year from a TDateTime value.
`DaysBetween`	function	Number of whole days between two TDateTime values.
`DaysInAMonth`	function	Number of days in a month of a certain year.
`DaysInAYear`	function	Number of days in a particular year.
`DaysInMonth`	function	Return the number of days in the month in which a date occurs.
`DaysInYear`	function	Return the number of days in the year in which a date occurs.
`DaySpan`	function	Calculate the approximate number of days between two TDateTime values.
`DecodeDateDay`	procedure	Decode a TDateTime value in year and year of day.
`DecodeDateMonthWeek`	procedure	Decode a TDateTime value in a month, week of month and day of week.
`DecodeDateTime`	procedure	Decode a TDateTime value in a date and time value.
`DecodeDateWeek`	procedure	Decode a TDateTime value in a week of year and day of week.
`DecodeDayOfWeekInMonth`	procedure	Decode a TDateTime value in year, month, day of week parts.
`DosDateTimeToDateTime`	function	Convert DOS date/time format to TDateTime format.
`EncodeDateDay`	function	Encodes a year and day of year to a TDateTime value.
`EncodeDateMonthWeek`	function	Encodes a year, month, week of month and day of week to a TDateTime value.
`EncodeDateTime`	function	Encodes a TDateTime value from all its parts.
`EncodeDateWeek`	function	Encode a TDateTime value from a year, week and day of week triplet.
`EncodeDayOfWeekInMonth`	function	Encodes a year, month, week, day of week specification to a TDateTime value.
`EncodeTimeInterval`	function	Encode an interval as a TDateTime value.
`EndOfADay`	function	Calculates a TDateTime value representing the end of a specified day.
`EndOfAMonth`	function	Calculate a TDateTime value representing the last day of the indicated month.
`EndOfAWeek`	function	Return the last moment of day of the week, given a year and a week in the year.
`EndOfAYear`	function	Calculate a TDateTime value representing the last day of a year.
`EndOfTheDay`	function	Calculate a TDateTime value that represents the end of a given day.
`EndOfTheMonth`	function	Calculate a TDateTime value representing the last day of the month, given a day in that month.
`EndOfTheWeek`	function	Calculate a TDateTime value which represents the end of a week, given a date in that week.
`EndOfTheYear`	function	Calculate a TDateTime value representing the last day of a year, given a date in that year.
`HourOf`	function	Extract the hour part from a TDateTime value.
`HourOfTheDay`	function	Calculate the hour of a given TDateTime value.
`HourOfTheMonth`	function	Calculate the number of hours passed since the start of the month.
`HourOfTheWeek`	function	Calculate the number of hours elapsed since the start of the week.
`HourOfTheYear`	function	Calculate the number of hours passed since the start of the year.
`HoursBetween`	function	Calculate the number of whole hours between two TDateTime values.
`HourSpan`	function	Calculate the approximate number of hours between two TDateTime values.
`IncDay`	function	Increase a TDateTime value with a number of days.
`IncHour`	function	Increase a TDateTime value with a number of hours.
`IncMilliSecond`	function	Increase a TDateTime value with a number of milliseconds.
`IncMinute`	function	Increase a TDateTime value with a number of minutes.
`IncSecond`	function	Increase a TDateTime value with a number of seconds.
`IncWeek`	function	Increase a TDateTime value with a number of weeks.
`IncYear`	function	Increase a TDateTime value with a number of years.
`InvalidDateDayError`	procedure	Raise an EConvertError exception when a day is not a valid day of a year.
`InvalidDateMonthWeekError`	procedure	Raise an EConvertError exception when a Year,Month,WeekOfMonth,DayofWeek is invalid.
`InvalidDateTimeError`	procedure	Raise an EConvertError about an invalid date-time specification.
`InvalidDateWeekError`	procedure	Raise an EConvertError with an invalid Year, WeekOfyear and DayOfWeek specification.
`InvalidDayOfWeekInMonthError`	procedure	Raise an EConvertError exception when a Year,Month,NthDayofWeek,DayofWeek is invalid.
`IsAM`	function
`IsInLeapYear`	function	Determine whether a date is in a leap year.
`ISO8601ToDate`	function	Converts a date/time value in ISO 8601 notation to a native TDateTime type.
`ISO8601ToDateDef`	function	Converts an ISO 8601 date/time string to a TDateTime type.
`IsPM`	function	Determine whether a time is PM or AM.
`IsSameDay`	function	Check if two date/time indications are the same day.
`IsSameMonth`	function	Check if 2 dates are in the same month.
`IsToday`	function	Check whether a given date is today.
`IsValidDate`	function	Check whether a set of values is a valid date indication.
`IsValidDateDay`	function	Check whether a given year/day of year combination is a valid date.
`IsValidDateMonthWeek`	function	Check whether a given year/month/week/day of the week combination is a valid day.
`IsValidDateTime`	function	Check whether a set of values is a valid date and time indication.
`IsValidDateWeek`	function	Check whether a given year/week/day of the week combination is a valid day.
`IsValidTime`	function	Check whether a set of values is a valid time indication.
`JulianDateToDateTime`	function	Convert a Julian date representation to a TDateTime value.
`LocalTimeToUniversal`	function	Convert local time to UTC time.
`MacTimeStampToUnix`	function	Convert a Mac timestamp to a Unix timestamp.
`MacToDateTime`	function	Convert a Mac timestamp to a TDateTime timestamp.
`MilliSecondOf`	function	Extract the millisecond part from a TDateTime value.
`MilliSecondOfTheDay`	function	Calculate the number of milliseconds elapsed since the start of the day.
`MilliSecondOfTheHour`	function	Calculate the number of milliseconds elapsed since the start of the hour.
`MilliSecondOfTheMinute`	function	Calculate the number of milliseconds elapsed since the start of the minute.
`MilliSecondOfTheMonth`	function	Calculate number of milliseconds elapsed since the start of the month.
`MilliSecondOfTheSecond`	function	Calculate the number of milliseconds elapsed since the start of the second.
`MilliSecondOfTheWeek`	function	Calculate the number of milliseconds elapsed since the start of the week.
`MilliSecondOfTheYear`	function	Calculate the number of milliseconds elapsed since the start of the year.
`MilliSecondsBetween`	function	Calculate the number of whole milliseconds between two TDateTime values.
`MilliSecondSpan`	function	Calculate the approximate number of milliseconds between two TDateTime values.
`MinuteOf`	function	Extract the minute part from a TDateTime value.
`MinuteOfTheDay`	function	Calculate the number of minutes elapsed since the start of the day.
`MinuteOfTheHour`	function	Calculate the number of minutes elapsed since the start of the hour.
`MinuteOfTheMonth`	function	Calculate number of minutes elapsed since the start of the month.
`MinuteOfTheWeek`	function	Calculate the number of minutes elapsed since the start of the week.
`MinuteOfTheYear`	function	Calculate the number of minutes elapsed since the start of the year.
`MinutesBetween`	function	Calculate the number of whole minutes between two TDateTime values.
`MinuteSpan`	function	Calculate the approximate number of minutes between two TDateTime values.
`ModifiedJulianDateToDateTime`	function	Convert a modified Julian date representation to a TDateTime value.
`MonthOf`	function	Extract the month from a given date.
`MonthOfTheYear`	function	Extract the month of a TDateTime indication.
`MonthsBetween`	function	Calculate the number of whole months between two TDateTime values.
`MonthSpan`	function	Calculate the approximate number of months between two TDateTime values.
`NthDayOfWeek`	function	Calculate which occurrence of weekday in the month a given day represents.
`PeriodBetween`	procedure	Return the period (in years, months, days) between two dates.
`PreviousDayOfWeek`	function	Given a day of the week, return the previous day of the week.
`RecodeDate`	function	Replace date part of a TDateTime value with another date.
`RecodeDateTime`	function	Replace selected parts of a TDateTime value with other values.
`RecodeDay`	function	Replace day part of a TDateTime value with another day.
`RecodeHour`	function	Replace hours part of a TDateTime value with another hour.
`RecodeMilliSecond`	function	Replace milliseconds part of a TDateTime value with another millisecond.
`RecodeMinute`	function	Replace minutes part of a TDateTime value with another minute.
`RecodeMonth`	function	Replace month part of a TDateTime value with another month.
`RecodeSecond`	function	Replace seconds part of a TDateTime value with another second.
`RecodeTime`	function	Replace time part of a TDateTime value with another time.
`RecodeYear`	function	Replace year part of a TDateTime value with another year.
`SameDate`	function	Check whether two TDateTime values have the same date part.
`SameDateTime`	function	Check whether two TDateTime values have the same date and time parts.
`SameTime`	function	Check whether two TDateTime values have the same time part.
`ScanDateTime`	function	Scans a string for a TDateTime pattern and returns the date/time.
`SecondOf`	function	Extract the second part from a TDateTime value.
`SecondOfTheDay`	function	Calculate the number of seconds elapsed since the start of the day.
`SecondOfTheHour`	function	Calculate the number of seconds elapsed since the start of the hour.
`SecondOfTheMinute`	function	Calculate the number of seconds elapsed since the start of the minute.
`SecondOfTheMonth`	function	Calculate number of seconds elapsed since the start of the month.
`SecondOfTheWeek`	function	Calculate the number of seconds elapsed since the start of the week.
`SecondOfTheYear`	function	Calculate the number of seconds elapsed since the start of the year.
`SecondsBetween`	function	Calculate the number of whole seconds between two TDateTime values.
`SecondSpan`	function	Calculate the approximate number of seconds between two TDateTime values.
`StartOfADay`	function	Returns the start of a day as a TDateTime value, given a day indication.
`StartOfAMonth`	function	Return first date of month, given a year/month pair.
`StartOfAWeek`	function	Return a day of the week, given a year, week and day in the week.
`StartOfAYear`	function	Return the first day of a given year.
`StartOfTheDay`	function	Calculate the start of the day as a TDateTime value, given a moment in the day.
`StartOfTheMonth`	function	Calculate the first day of the month, given a date in that month.
`StartOfTheWeek`	function	Return the first day of the week, given a date.
`StartOfTheYear`	function	Return the first day of the year, given a date in this year.
`TimeInRange`	function	Checks whether a time value is in a given range.
`TimeOf`	function	Extract the time part from a TDateTime indication.
`Today`	function	Return the current date.
`Tomorrow`	function	Return the next day after today.
`TryEncodeDateDay`	function	Encode a year and day of year to a TDateTime value.
`TryEncodeDateMonthWeek`	function	Encode a year, month, week of month and day of week to a TDateTime value.
`TryEncodeDateTime`	function	Encode a Year, Month, Day, Hour, minute, seconds, milliseconds tuplet to a TDateTime value.
`TryEncodeDateWeek`	function	Encode a year, week and day of week triplet to a TDateTime value.
`TryEncodeDayOfWeekInMonth`	function	Encode a year, month, week, day of week triplet to a TDateTime value.
`TryEncodeTimeInterval`	function	Try to encode an interval as a TDateTime value.
`TryISO8601ToDate`	function	Attempts to convert an ISO 8601-formatted date/time value to a TDateTime type.
`TryISOStrToDate`	function	Attempts to convert an ISO 8601-formatted date value to a TDateTime type.
`TryISOStrToDateTime`	function	Attempts to convert an ISO 8601-formatted date/time value to a TDateTime type.
`TryISOStrToTime`	function	Converts an ISO 8601-formatted time value to a TDateTime type.
`TryISOTZStrToTZOffset`	function	Attempts to convert an ISO 8601 time zone designation to an offset in minutes.
`TryJulianDateToDateTime`	function	Convert a Julian date representation to a TDateTime value.
`TryModifiedJulianDateToDateTime`	function	Convert a modified Julian date representation to a TDateTime value.
`TryRecodeDateTime`	function	Replace selected parts of a TDateTime value with other values.
`UniversalTimeToLocal`	function	Convert UTC time to local time.
`UnixTimeStampToMac`	function	Convert Unix Timestamp to a Mac Timestamp.
`UnixToDateTime`	function	Convert Unix epoch time to a TDateTime value.
`WeekOf`	function	Extract week (of the year) from a given date.
`WeekOfTheMonth`	function	Extract the week of the month (and optionally month and year) from a TDateTime value.
`WeekOfTheYear`	function	Extract the week of the year (and optionally year) of a TDateTime indication.
`WeeksBetween`	function	Calculate the number of whole weeks between two TDateTime values.
`WeeksInAYear`	function	Returns the number of weeks in a given year.
`WeeksInYear`	function	Returns the number of weeks in the year, given a date.
`WeekSpan`	function	Calculate the approximate number of weeks between two TDateTime values.
`WithinPastDays`	function	Check whether two TDateTimes are only a number of days apart.
`WithinPastHours`	function	Check whether two TDateTimes are only a number of hours apart.
`WithinPastMilliSeconds`	function	Check whether two TDateTimes are only a number of milliseconds apart.
`WithinPastMinutes`	function	Check whether two TDateTimes are only a number of minutes apart.
`WithinPastMonths`	function	Check whether two TDateTimes are only a number of months apart.
`WithinPastSeconds`	function	Check whether two TDateTimes are only a number of seconds apart.
`WithinPastWeeks`	function	Check whether two TDateTimes are only a number of weeks apart.
`WithinPastYears`	function	Check whether two TDateTimes are only a number of years apart.
`YearOf`	function	Extract the year from a given date.
`YearsBetween`	function	Calculate the number of whole years between two TDateTime values.
`YearSpan`	function	Calculate the approximate number of years between two TDateTime values.
`Yesterday`	function	Return the previous day.

Types

TLocalTimeType enumeration

Constants

`ApproxDaysPerMonth`	constant	Average number of days in a month, measured over a year. Used in .
`ApproxDaysPerYear`	constant	Average number of days in a year, measured over 4 years. Used in .
`DateTimeEpsilon`	constant
`DayFriday`	constant	ISO day number for Friday.
`DayMonday`	constant	ISO day number for Monday.
`DaySaturday`	constant	ISO day number for Saturday.
`DaysPerWeek`	constant	Number of days in a week.
`DaysPerYear`	constant	Array with number of days in a year. The Boolean index indicates whether it is a leap year or not.
`DaySunday`	constant	ISO day number for Sunday.
`DayThursday`	constant	ISO day number for Thursday.
`DayTuesday`	constant	ISO day number for Tuesday.
`DayWednesday`	constant	ISO day number for Wednesday.
`MonthApril`	constant	ISO month number for April.
`MonthAugust`	constant	ISO month number for August.
`MonthDecember`	constant	ISO month number for December.
`MonthFebruary`	constant	ISO month number for february.
`MonthJanuary`	constant	ISO month number for january.
`MonthJuly`	constant	ISO month number for July.
`MonthJune`	constant	ISO month number for June.
`MonthMarch`	constant	ISO month number for March.
`MonthMay`	constant	ISO month number for May.
`MonthNovember`	constant	ISO month number for November.
`MonthOctober`	constant	ISO month number for October.
`MonthSeptember`	constant	ISO month number for September.
`MonthsPerYear`	constant	Number of months in a year.
`OneHour`	constant	One hour as a fraction of a day (suitable for TDateTime).
`OneMillisecond`	constant	One millisecond as a fraction of a day (suitable for TDateTime).
`OneMinute`	constant	One minute as a fraction of a day (suitable for TDateTime).
`OneSecond`	constant	One second as a fraction of a day (suitable for TDateTime).
`RecodeLeaveFieldAsIs`	constant	Bitmask deciding what to do with each TDateTime field in recode routines.
`WeeksPerFortnight`	constant	Number of weeks in fortnight.
`YearsPerCentury`	constant	Number of years in a century.
`YearsPerDecade`	constant	Number of years in a decade.
`YearsPerMillennium`	constant	Number of years in a millennium.

Uses

sysutils
Math
System.TimeSpan

An experiment, built from development snapshots. Not the official Free Pascal or Lazarus documentation.