Add date stamp to time stamp

Question

vicsm 2019-11-1

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https://ww2.mathworks.cn/matlabcentral/answers/488724-add-date-stamp-to-time-stamp

评论： vicsm 2019-11-1

BB.mat

Hi,

I have a 270176x15 table (see attached a reduced version of it, called BB.mat) where one of my arrays is Time (with measurements every second). Date stamp is missing, and I have two questions about this:

1) How can I add the date stamp (Date) that changes accordingly to my Time (i.e. changes day from 23:59 to 00:00) IF

2) (IF) the only date reference I have is: my last timestamp (i.e. 16:05:07) corresponds to 21/05/2018? (so basically I know the end date but not the start date).

Does anyone know how to do this? Any help will be very much appreciated!

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Answer 1

Guillaume 2019-11-1

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Here's how I'd do it. Whatever you do don't use outdated datenum and datestr. Stay with datetime and duration arrays.

[h, m, s] = hms(HRV_BB3.Time(end));  %extract hours, minutes and seconds from last time (actually a datetime whose date is wrong)
enddate = datetime(2018,5,21,h,m,s)  %calculate the right datetime
HRV_BB3.DateTime = enddate + [cumsum(-mod(diff(HRV_BB3.Time), hours(24)), 'reverse'); 0];  %calculate difference between consecutive dates, modulo 24h, and add that back

Done!

This assumes of course that days aren't skipped. But since you've lost that information, there's no way to know.

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vicsm 2019-11-1

THANK YOU so much! This solved my problem completely!

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Answer 2

Sulaymon Eshkabilov 2019-11-1

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Hi,

these commands will resolve your task:

load BB
EEE=datenum(HRV_BB3.Time);
DATES = datestr(EEE, 'mm/dd/yy');

You'd need to adjust the starting day or end day.

Good luck.

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Sulaymon Eshkabilov 2019-11-1

编辑：Sulaymon Eshkabilov 2019-11-1

The data you have provided BB.mat works very well. Probably the data (mat file) you are using is different from the one you have provided here - BB.mat

vicsm 2019-11-1

编辑：vicsm 2019-11-1

But the date doesn't change from 23:59:59 to 00:00:00; it's still 10/30/19 and instead it should be 11/01/19. Maybe I'm not explaining myself properly...

I need it to look like this:

23:59:56 10/30/19

23:59:57 10/30/19

23:59:58 10/30/19

23:59:59 10/30/19

00:00:00 11/01/19

00:00:01 11/01/19

00:00:02 11/01/19

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