datenum

Convert date and time to serial date number

The datenum function creates a numeric array that represents each point in time as the number of days from January 0, 0000. The numeric values also can represent elapsed time in units of days. However, the best way to represent points in time is by using the datetime data type. The best way to represent elapsed time is by using the duration or calendarDuration data types.

Syntax

DateNumber = datenum(t)

DateNumber = datenum(DateString)

DateNumber = datenum(DateString,formatIn)

DateNumber = datenum(DateString,PivotYear)

DateNumber = datenum(DateString,formatIn,PivotYear)

DateNumber = datenum(DateVector)

DateNumber = datenum(Y,M,D)

DateNumber = datenum(Y,M,D,H,MN,S)

Description

DateNumber = datenum(t) converts the datetime or duration values in the input array t to serial date numbers.

A serial date number represents the whole and fractional number of days from a fixed, preset date (January 0, 0000) in the proleptic ISO calendar.

DateNumber = datenum(DateString) converts text representing dates and times to serial date numbers. If the format used in the text is known, specify the format as formatIn. Syntaxes without formatIn are significantly slower than syntaxes that include it.

DateNumber = datenum(DateString,formatIn) uses formatIn to interpret the dates and times represented by DateString.

DateNumber = datenum(DateString,PivotYear) uses PivotYear to interpret text that specifies the year as two characters. If the format used in the text is known, specify the format as formatIn. Syntaxes without formatIn are significantly slower than syntaxes that include it.

DateNumber = datenum(DateString,formatIn,PivotYear) uses formatIn to interpret the dates and times represented by DateString, and PivotYear to interpret text that specifies the year as two characters. You can specify formatIn and PivotYear in either order.

DateNumber = datenum(DateVector) converts date vectors to serial date numbers, and returns a column vector of m date numbers, where m is the total number of date vectors in DateVector.

DateNumber = datenum(Y,M,D) returns the serial date numbers for corresponding elements of the Y, M, and D (year, month, day) arrays. The arrays must be of the same size (or any can be a scalar). You also can specify the input arguments as a date vector, [Y,M,D].

DateNumber = datenum(Y,M,D,H,MN,S) additionally returns the serial date numbers for corresponding elements of the H, MN, and S (hour, minute, and second) arrays. The arrays must be of the same size (or any can be a scalar). You also can specify the input arguments as a date vector, [Y,M,D,H,MN,S].

Examples

Convert datetime Array to Date Numbers

format long 

t = [datetime('now');datetime('tomorrow')]

t = 2x1 datetime array
   27-Aug-2018 13:31:08
   28-Aug-2018 00:00:00

DateNumber = datenum(t)

DateNumber = 2×1
105 ×

   7.372995632963565
   7.373000000000000

Convert Text Representing Date to Date Number

DateString = '19-May-2001';
formatIn = 'dd-mmm-yyyy';
datenum(DateString,formatIn)

ans = 730990

datenum returns a date number for text representing a date with the format 'dd-mmm-yyyy'.

Convert Text with Multiple Dates to Date Numbers

Pass several dates as character vectors in a cell array. All input dates must use the same format.

DateString = {'09/16/2007';'05/14/1996';'11/29/2010'};
formatIn = 'mm/dd/yyyy';
datenum(DateString,formatIn)

ans = 3×1

      733301
      729159
      734471

Convert Text Representing Date to Date Number Using Pivot Year

Convert text representing a date to a serial date number using the default pivot year.

n = datenum('12-jun-17','dd-mmm-yy')

n = 736858

The text that represents this date number is '12-Jun-2017'.

Convert the same text to a serial date number using 1400 as the pivot year.

n = datenum('12-jun-17','dd-mmm-yy',1400)

n = 517712

The text that represents this date number is '12-Jun-1417'.

Convert Date Vector to Date Number

datenum([2009,4,2,11,7,18])

ans = 7.3387e+05

Convert Year, Month, and Day to Date Number

Convert a date specified by year, month and day values to a serial date number.

n = datenum(2001,12,19)

n = 731204

Input Arguments

t — Dates and times

array of datetime or duration values

Dates and times, specified as an array of datetime or duration values. The datenum function does not account for time zone information in t and does not adjust datetime values that occur during Daylight Saving Time. That is, datenum treats the TimeZone property of datetime arrays as empty and converts the remaining date and time information to a serial date number.

Data Types: datetime | duration

DateVector — Date vectors

matrix

Date vectors, specified as an m-by-6 or m-by-3 matrix containing m full or partial date vectors, respectively. A full date vector has six elements, specifying year, month, day, hour, minute, and second, in that order. A partial date vector has three elements, specifying year, month, and day, in that order. Each element of DateVector must be a positive or negative integer value except for the seconds element, which can be fractional. If an element falls outside the conventional range, datenum adjusts both that date vector element and the previous element. For example, if the minutes element is 70, then datenum adjusts the hours element by 1 and sets the minutes element to 10. If the minutes element is -15, then datevec decreases the hours element by 1 and sets the minutes element to 45. Month values are an exception. The datenum function sets month values less than 1 to 1.

Example: [2003,10,24,12,45,07]

Data Types: double

DateString — Text representing dates and times

character array | cell vector of character vectors | string vector

Text representing dates and times, specified as a character array where each row contains text representing one point in time, as a cell vector of character vectors, or as a string vector. All rows of a character array, or all elements of a cell vector or string vector, must have the same format.

Example: '24-Oct-2003 12:45:07'

Example: ['19-Sep-2013';'20-Sep-2013';'21-Sep-2013']

Example: {'15-Oct-2010' '20-Nov-2012'}

If the format used in the text is known, you should also specify formatIn. If you do not specify formatIn, then DateString must be in one of the following formats.

Format of Text Representing Dates and Times	Example
'dd-mmm-yyyy HH:MM:SS'	01-Mar-2000 15:45:17
'dd-mmm-yyyy'	01-Mar-2000
'mm/dd/yyyy'	03/01/2000
'mm/dd/yy'	03/01/00
'mm/dd'	03/01
'mmm.dd,yyyy HH:MM:SS'	Mar.01,2000 15:45:17
'mmm.dd,yyyy'	Mar.01,2000
'yyyy-mm-dd HH:MM:SS'	2000-03-01 15:45:17
'yyyy-mm-dd'	2000-03-01
'yyyy/mm/dd'	2000/03/01
'HH:MM:SS'	15:45:17
'HH:MM:SS PM'	3:45:17 PM
'HH:MM'	15:45
'HH:MM PM'	3:45 PM

Note

The symbolic identifiers describing date and time formats are different from those that describe the display formats of datetime arrays.

Certain formats might not contain enough information to convert text representations of dates and times. In those cases, hours, minutes, and seconds default to 0, days default to 1, months default to January, and years default to the current year. datevec and datenum consider two-character years (e.g., '79') to fall within the 100-year range centered around the current year.

When you do not specify formatIn, note the following:

• For the formats that specify the month as two digits (mm), the month value must not be greater than 12.

• However, for the format 'mm/dd/yy', if the first entry in the text is greater than 12 and the second entry is less than or equal to 12, then datenum considers the text to be in 'yy/mm/dd' format.

formatIn — Format of input text representing dates and times

character vector | string scalar

Format of the input text representing dates and times, specified as a character vector or string scalar of symbolic identifiers.

Example: 'dddd, mmm dd, yyyy'

The following table shows symbolic identifiers that you can use to construct the formatIn character vector. You can include characters such as a hyphen, space, or colon to separate the fields.

Note

The symbolic identifiers describing date and time formats are different from the identifiers that describe the display formats of datetime arrays.

Symbolic Identifier	Description	Example
yyyy	Year in full	1990, 2002
yy	Year in two digits	90, 02
QQ	Quarter year using letter Q and one digit	Q1
mmmm	Month using full name	March, December
mmm	Month using first three letters	Mar, Dec
mm	Month in two digits	03, 12
m	Month using capitalized first letter	M, D
dddd	Day using full name	Monday, Tuesday
ddd	Day using first three letters	Mon, Tue
dd	Day in two digits	05, 20
d	Day using capitalized first letter	M, T
HH	Hour in two digits (no leading zeros when symbolic identifier AM or PM is used)	05, 5 AM
MM	Minute in two digits	12, 02
SS	Second in two digits	07, 59
FFF	Millisecond in three digits	057
AM or PM	AM or PM inserted in text representing time	3:45:02 PM

The formatIn value must follow these guidelines:

• You cannot specify any field more than once. For example, you cannot use 'yy-mmm-dd-m' because it has two month identifiers. The one exception to this is that you can combine one instance of dd with one instance of any of the other day identifiers. For example, 'dddd mmm dd yyyy' is a valid input.

• When you use AM or PM, the HH field is also required.

• You only can use QQ alone or with a year specifier.

PivotYear — Start year of 100-year date range

present minus 50 years (default) | integer

Start year of the 100-year date range in which a two-character year resides, specified as an integer. Use a pivot year to interpret dates that specify the year as two characters.

If formatIn contains the time of day, the pivot year is computed from the current time of the current day, month, and year. Otherwise it is computed from midnight of the current day, month, and year.

Example: 2000

Note

If the input date format specifies a four-character year, then the last two characters are truncated, and the first two characters specify the year. For example, if the date and pivot year are specified as ('25122015','ddmmyyyy',2000), then the resulting date is 25-12-2020, not 25-12-2015.

Data Types: double

Y,M,D — Year, month, and day arrays

numeric arrays

Year, month, and day arrays specified as numeric arrays. These arrays must be the same size, or any one can be a scalar. The values in Y,M,D must be integer values.

If Y,M,D are all scalars or all column vectors, you can specify the input arguments as a date vector, [Y,M,D].

Example: 2003,10,24

Data Types: double

Y,M,D,H,MN,S — Year, month, day, hour, minute, and second arrays

numeric arrays

Year, month, day, hour, minute, and second arrays specified as numeric arrays. These arrays must be the same size, or any one can be a scalar. datenum does not accept milliseconds as a separate input, but as a fractional part of the seconds input, S. The values in Y,M,D,H,MN must be integer values.

If Y,M,D,H,MN,S are all scalars or all column vectors, you can specify the input arguments as a date vector, [Y,M,D,H,MN,S].

Example: 2003,10,24,12,45,07.451

Data Types: double

Output Arguments

DateNumber — Serial date numbers

scalar | vector

Serial date numbers, returned as a column vector of length m, where m is the total number of input date vectors or character vectors representing dates and times.

Tips

• To create arbitrarily shaped output, use the datenum(Y,M,D) and datenum(Y,M,D,H,MN,S) syntaxes. The datenum(DateVector) syntax creates only a column vector of date numbers.

  datenum(2013,[1 3; 2 4],ones(2,2))

  ans =
  
        735235      735294
        735266      735325

Extended Capabilities

Tall Arrays

Calculate with arrays that have more rows than fit in memory.

This function fully supports tall arrays. For more information, see Tall Arrays.

Distributed Arrays

Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

This function fully supports distributed arrays. For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).