Datetime differences but ignoring years

I have a bunch of datetimes and I want to know the times between them, but I don't want to consider the year. So, say the dates are:

2019-11-29 09:00:00

2020-11-20 10:10:00

2021-11-22 08:30:00

The order I want to sort these into when ignoring the year would be:

11-20 10:00:00

11-22 08:30:00

11-29 09:00:00

Then I want the time between these in minutes, so [2790,10110] if I did my math right. What's the easiest way to do this?

Answer 1

[Cris LaPierre]

You can't just drop the year from a datetime variable. It's there, even if your viewing format does not display it. To me, that suggests either making the year the same in all of your datetimes, or sort by month of year, then day of month, then hour, etc.

I think changing the year is easiest, especially since your minutes are calculated ignoring year as well. You can use the functions diff and minutes to find the time between each datetime.

T = datetime([2019 11 29 09 00 00; 2020 11 20 10 10 00; 2121 11 22 08 30 00])

T = 3×1 datetime array
   29-Nov-2019 09:00:00
   20-Nov-2020 10:10:00
   22-Nov-2121 08:30:00

Ttemp = T;
Ttemp.Format = 'MM-dd HH:mm:ss';
Ttemp.Year = 2020

Ttemp = 3×1 datetime array
   11-29 09:00:00
   11-20 10:10:00
   11-22 08:30:00

Tnew = sort(Ttemp)

Tnew = 3×1 datetime array
   11-20 10:10:00
   11-22 08:30:00
   11-29 09:00:00

dmin = minutes(diff(Tnew))

dmin = 2×1

2780 10110

[Dan Houck]

This is basically what I did. It would definitely be trickier if the dates went over 2/29 in some years. Thanks!

[Peter Perkins]

Yes. The problem is that your question is ill-posed. In general you can't ignore the year. Especially if there are DST timezones involved. But if the timestamps don't straddle a leap day, and you don't care about DST shifts, Cris has the right way to go.