({{, (RefLink[AbsoluteTime, paclet:ref/AbsoluteTime])[]
gives the total number of seconds since the beginning of January 1, 1900, in your time zone.}, {, (RefLink[AbsoluteTime, paclet:ref/AbsoluteTime])[{y,m,d,h,m,s}] 
gives the absolute time specification corresponding to a date list. }, {, (RefLink[AbsoluteTime, paclet:ref/AbsoluteTime])[date]
gives the absolute time specification corresponding to a (RefLink[DateObject, paclet:ref/DateObject]).}, {, (RefLink[AbsoluteTime, paclet:ref/AbsoluteTime])["string"] 
gives the absolute time specification corresponding to a date string.}, {, (RefLink[AbsoluteTime, paclet:ref/AbsoluteTime])[{"string",{"(Subscript[e, 1])","(Subscript[e, 2])",…}}] 
takes the date string to contain the elements "(Subscript[e, i])".}})

OpenersNotesSection(Spacer1)Details and Options

(RefLink[AbsoluteTime, paclet:ref/AbsoluteTime])[] uses whatever date and time have been set on your computer system. It performs no corrections for time zones, daylight saving time, etc.

(RefLink[AbsoluteTime, paclet:ref/AbsoluteTime])[(RefLink[TimeZone, paclet:ref/TimeZone]) -> z] gives the date and time inferred for time zone z by assuming that your computer is set for the time zone specified by (RefLink[$TimeZone, paclet:ref/$TimeZone]). »

(RefLink[AbsoluteTime, paclet:ref/AbsoluteTime])[] is always accurate down to a granularity of (RefLink[$TimeUnit, paclet:ref/$TimeUnit]) seconds, but on many systems is much more accurate.

Shorter lists can be used in (RefLink[AbsoluteTime, paclet:ref/AbsoluteTime])[{y,m,…}]: {y} is equivalent to {y,1,1,0,0,0}, {y,m} to {y,m,1,0,0,0}, etc.

Values of m, d, h, m, s outside their normal ranges are appropriately reduced. Noninteger values of d, h, m, s can also be used. »

OpenersPrimaryExamplesSection(Spacer1)Examples  (17)

OpenersExampleSection0(Spacer1)Basic Examples  (5)

Absolute time in seconds since January 1, 1900:

AbsoluteTime[]

Convert from a date object to an absolute time:

AbsoluteTime[(DateObject["Day: ""Thu 18 Dec 2014", DateObject[{2014,12,18},"Day","Gregorian",-6.`]])]

Convert a date list or elided date list:

AbsoluteTime[{2007,1,1,0,0,0}]

AbsoluteTime[{2007,1}]

Convert from a date string to absolute time:

DateString[]

AbsoluteTime[%]

Specify date elements for interpreting a string:

AbsoluteTime[{"05/06/07",{"Day","Month","YearShort"}}]

OpenersExampleSection1(Spacer1)Scope  (5)

Strings are automatically interpreted when possible:

AbsoluteTime["2006-12-1"]

AbsoluteTime["10 March 2006"]

Separators are assumed if not specified:

AbsoluteTime[{"2/23/2007",{"Month","Day","Year"}}]

Give explicit separators:

AbsoluteTime[{"2/23/2007",{"Month","/","Day","/","Year"}}]

Date lists are converted to standard normalized form:

AbsoluteTime[{2006,2,31}]

AbsoluteTime[{2006,3,3}]

Day, hour, minute, and second values in input date lists can be noninteger:

AbsoluteTime[{2007,3,15.5}]

AbsoluteTime[{2007,3,15,12.3}]

The current year is used if not specified in a string:

AbsoluteTime[{"2/15",{"Month","Day"}}]

OpenersExampleSection2(Spacer1)Generalizations & Extensions  (1)

Give explicit date elements to interpret ambiguous strings:

AbsoluteTime["05/10/1"]

AbsoluteTime[{"05/10/1",{"YearShort","Day","Month"}}]

OpenersExampleSection3(Spacer1)Options  (1)

OpenersExampleSubsection0(Spacer1)TimeZone  (1)

Find the current absolute time in Greenwich, United Kingdom:

AbsoluteTime[TimeZone->0]

Find the absolute time for a given date using a time zone string:

AbsoluteTime[{2015,8,4,9,14,2}, TimeZone->"America/New_York"]

OpenersExampleSection5(Spacer1)Properties & Relations  (5)

Compute the number of seconds between January 1, 1900, and January 1, 2000:

AbsoluteTime[{2000,1,1,0,0,0}]

(RefLink[AbsoluteTime, paclet:ref/AbsoluteTime]) represents dates as seconds since the beginning of 1900:

AbsoluteTime[(DateObject["Day: ""Mon 1 Jan 2007", DateObject[{2007,1,1},"Day","Gregorian",-6.`]])]

(RefLink[DateObject, paclet:ref/DateObject]) represents a given date:

DateObject[%]

(RefLink[DateList, paclet:ref/DateList]) represents dates as lists of date elements:

DateList[%]

(RefLink[DateString, paclet:ref/DateString]) represents dates as strings:

DateString[%]

Use (RefLink[DateListPlot, paclet:ref/DateListPlot]) to plot data with absolute time x coordinates on a time scale:

DateListPlot[{{3376598400,2},{3379276800,4},{3381696000,6},{3384374400,8}}]

(RefLink[UnixTime, paclet:ref/UnixTime]) returns the number of seconds since the beginning of 1970, in the GMT time zone:

UnixTime[]

Therefore this difference is constant:

IntegerPart[AbsoluteTime[TimeZone->0]-UnixTime[]]

It is the number of seconds since January 1, 1900, to January 1, 1970:

AbsoluteTime[{1970,1,1,0,0,0}]

(RefLink[JulianDate, paclet:ref/JulianDate]) returns the number of days since noon on November 24, 4714 BCE in the GMT time zone:

JulianDate[]

Therefore this difference is constant:

IntegerPart[86400JulianDate[]-AbsoluteTime[TimeZone->0]]

It is the number of seconds since noon on November 24, 4714, to the beginning of January 1, 1900:

AbsoluteTime[{-4714,11,24,12,0,0}]

({{DocumentationFooterIconsRelatedFunction.png, ({{See Also}, {(RefLink[UnixTime, paclet:ref/UnixTime])  ▪  (RefLink[DateList, paclet:ref/DateList])  ▪  (RefLink[DateString, paclet:ref/DateString])  ▪  (RefLink[DateObject, paclet:ref/DateObject])  ▪  (RefLink[JulianDate, paclet:ref/JulianDate])  ▪  (RefLink[FromAbsoluteTime, paclet:ref/FromAbsoluteTime])  ▪  (RefLink[DateValue, paclet:ref/DateValue])  ▪  (RefLink[Now, paclet:ref/Now])  ▪  (RefLink[SessionTime, paclet:ref/SessionTime])  ▪  (RefLink[TimeUsed, paclet:ref/TimeUsed])  ▪  (RefLink[Clock, paclet:ref/Clock])  ▪  (RefLink[AbsoluteTiming, paclet:ref/AbsoluteTiming])  ▪  (RefLink[Timing, paclet:ref/Timing])  ▪  (RefLink[TimeZone, paclet:ref/TimeZone])  ▪  (RefLink[$TimeUnit, paclet:ref/$TimeUnit])  ▪  (RefLink[DatePlus, paclet:ref/DatePlus])  ▪  (RefLink[DateDifference, paclet:ref/DateDifference])}})}})

({{DocumentationFooterIconsRelatedTutorial.png, ({{Tutorials}, {▪(RefLinkPlain[Date and Time Functions, paclet:tutorial/DateAndTimeFunctions])}, {▪(RefLinkPlain[Global System Information, paclet:tutorial/GlobalSystemInformation])}})}})

({{DocumentationFooterIconsRelatedGuide.png, ({{Related Guides}, {▪(RefLinkPlain[Date & Time, paclet:guide/DateAndTime])}, {▪(RefLinkPlain[External Operations, paclet:guide/ExternalOperations])}, {▪(RefLinkPlain[Time Measurement & Optimization, paclet:guide/TimeMeasurementAndOptimization])}, {▪(RefLinkPlain[Locale & Internationalization, paclet:guide/LocaleAndInternationalization])}, {▪(RefLinkPlain[Cloud Execution Metadata, paclet:guide/CloudExecutionMetadata])}, {▪(RefLinkPlain[Wolfram System Session Information, paclet:guide/WolframSystemSessionInformation])}})}})