Problem with transforming a string date to a datetime variable in Matlab

Question

I have a variable called FOUNDATION_DATE which includes the following date observations in string format:

'01/Jan/12'
''
''
''
'01/Jan/08'
''
'01/Jan/44'
''
''
'14/Oct/08'
''
''
'12/Jul/04'
'03/Aug/05'
'20/Apr/10'
'30/Dec/98'
'09/Apr/16'
'01/Jan/10'
'01/Dec/01'
'01/Jan/93'

I am using the Matlab function datetime to transform the above observations in datetime data type. The code is

datetime(FOUNDATION_DATE,'InputFormat','dd/MMM/yy')

which provides the following results:

01-Jan-2012
NaT
NaT
NaT
01-Jan-2008
NaT
01-Jan-2044
NaT
NaT
14-Oct-2008
NaT
NaT
12-Jul-2004
03-Aug-2005
20-Apr-2010
30-Dec-1998
09-Apr-2016
01-Jan-2010
01-Dec-2001
01-Jan-1993

While for the majority of the cases the transformation is conducted properly, for the observation '01/Jan/44' this is not the case as the year becomes 2044. This issue appears in many other date observations of my variable (only a small sample is presented here) and it is quite strange that this issue appears for date observations for years before 1969.

Does anyone have a solution for accurately transforming these strings to datetime variables? Any explanation also why this happens?

Have a look at the datetime help. There is an option called PivotYear, which says: Start year of the 100-year date range in which a two-character year resides [...] The default is year(datetime('now')) - 50 which is 1969 as of today. Set PivotYear to year(datetime('now')) - 99, and you should be fine. — HansHirse
– HansHirse, Commented Mar 7, 2019 at 15:55

Wolfie · Accepted Answer · 2019-03-07 15:57:19Z

4

You want the 'PivotYear' option, which defines which 100-year date range the 2 digit date refers to:

datetime( '01/Jan/44', 'inputformat', 'dd/MMM/yy', 'pivotyear', 1930 )

So here the 100-year range is 1930 - 2029

The default as documented (therefore not very "strange"), is

year(datetime('now'))-50 % = 1969 at time of writing (2019)

answered Mar 7, 2019 at 15:57

Wolfie

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2 Comments

Whitebeard13 Over a year ago

Is it possible to enlarge this 100-year range?

Wolfie Over a year ago

@Whitebeard13 Logically it's impossible - how would you expect Matlab to handle 2019 (written as just "19") if your date range was 1900 to 2099?

matlabgui · Accepted Answer · 2019-03-07 15:57:06Z

1

When only 2 years are represented matlab makes an assumption on what the first two digits are, you can override this by:

startYear = year(datetime('now')) - 99;
datetime('01/Jan/69', 'InputFormat', 'dd/MMM/yy', 'PivotYear', startYear)

That will make any dates in 2 digits up until today be historic.

answered Mar 7, 2019 at 15:57

matlabgui

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