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Can I get a datetime output in a different Time Zone from the input Time Zone in one function call?

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d = datetime('2016-Jan-20 12:00:00','TimeZone','UTC')
and then
d.TimeZone = 'America/New_York'
gets me the transformed time from the input... is there any way to get this answer in the original function call, without haveing the 2nd command? I know there is a Format option, but I cannot see how one can add a TimeZone in that. transform the input TimeZone.

Accepted Answer

Walter Roberson
Walter Roberson on 23 Jan 2017
d = subsasgn(datetime('2016-Jan-20 12:00:00','TimeZone','UTC'), struct('type', '.', 'subs', {'TimeZone'}), 'America/New_York');
You might want to create a help function for that, like
sset = @(var, sub, val) subsassgn(var, struct('type', '.', 'subs', {sub}), val);
and then
sset(datetime('2016-Jan-20 12:00:00','TimeZone','UTC'), 'TimeZone', 'America/New_York')
datetimeNY = @(date) subsasgn( datetime(date, 'TimeZone', 'UTC'), struct('type', '.', 'subs', {'TimeZone'}), 'America/New_York');
which you could then use as
d = datetimeNY('2016-Jan-20 12:00:00');
  1 Comment
Jeff Waldron
Jeff Waldron on 23 Jan 2017
Thank you... that's great... I have seen subsasgn in a couple other answers on other topics, but I've never used it, and thus always forget about it's capabilitities... Appreciate the direction.

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More Answers (2)

Peter Perkins
Peter Perkins on 23 Jan 2017
I think this also does what you want:
>> d = datetime('2016-Jan-20 12:00:00 UTC','InputFormat','yyyy-MMM-dd HH:mm:ss z','TimeZone','America/New_York')
d =
20-Jan-2016 07:00:00
but it requires that 'UTC' be appended to each timestamp. So choose your poison: is calling subsasgn directly better or worse? The only reason I can think to need one line is that you're writing an anonymous function.

Maitreyee Mordekar
Maitreyee Mordekar on 23 Jan 2017
Hi Jeff,
The following command will help you set the desired functionality-
d = datetime('2016-Jan-20 12:00:00','TimeZone','America/New_York');
The following link is the reference documentation for 'datatime' function-
Peter Perkins
Peter Perkins on 23 Jan 2017
Just to expand a bit on this:
If you assign the TimeZone property of an unzoned datetime, the result will "look" the same, in other words, it becomes the same clockface time in a specific time zone.
On the other hand, if you assign the TimeZone property of a datetime that's already in a specific time zone, the instant in time remains the same, but it "looks" different because of the different time zone offsets. So what Walter is saying is that creating a datetime at 12pm in UTC, and then setting its TimeZone property to America/New_York results in 7am, New York time. Same instant, different timestamp.

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