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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(DateString)
  • DateNumber = datenum(DateString,formatIn)
    example
  • DateNumber = datenum(DateString,PivotYear)
  • DateNumber = datenum(DateString,formatIn,PivotYear)
    example
  • DateNumber = datenum(DateVector)
    example
  • DateNumber = datenum(Y,M,D)
    example
  • DateNumber = datenum(Y,M,D,H,MN,S)

Description

example

DateNumber = datenum(t) converts the datetime values in datetime 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.

example

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.

example

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.

example

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.

example

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

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format long

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

  2×1 datetime array

   30-Aug-2016 15:26:38
   31-Aug-2016 00:00:00


DateNumber =

   1.0e+05 *

   7.365726435003211
   7.365730000000000

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'.

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 =

      733301
      729159
      734471

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'.

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

   7.3387e+05

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

n = datenum(2001,12,19)
n =

      731204

Input Arguments

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datetime values, specified as a scalar, vector, matrix, or multidimensional datetime array. datenum 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 t as empty and converts the remaining date and time information to a serial date number.

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 should 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, 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. datenum sets month values less than 1 to 1.

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

Data Types: double

Text representing dates and times, specified as a character array where each row contains text representing one point in time, or as a one dimensional cell array of character vectors. All rows of a character array, or all elements of a cell array, 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, 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.

Format of the input text representing dates and times, specified as a character vector 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.

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

Year, month, and day arrays specified as a scalar, vector, matrix, or array. These must be the same size, or any one can be a scalar. Y,M,D should 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

Year, month, day, hour, minute, and second arrays specified as a scalar, vector, matrix, or array. These 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. Y,M,D,H,MN should 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

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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.

More About

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Tall Array Support

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

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

See Also

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Introduced before R2006a

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