Date/Time Manipulation

RobertJ has asked for the wisdom of the Perl Monks concerning the following question:

Hello, been a while since my last visit.

Looking for a simple (hopefully) way of subtracting one hour from date - time in a file.

The file is a text file of the following format:

2016-05-16 10:51:07 random text1

2016-05-16 11:58:37 random text2

2016-05-16 12:01:49 random text3

All the times are during the daytime so I do not have to worry about "role-over" at midnight.

I simply want to change the above to

2016-05-16 09:51:07 random text1

2016-05-16 10:58:37 random text2

2016-05-16 11:01:49 random text3

I have BBEdit which will run Perl and on a Mac with the latest Perl modules that come with the OS.

Comment on Date/Time Manipulation

Replies are listed 'Best First'.
Re: Date/Time Manipulation by johngg (Canon) on May 24, 2016 at 18:50 UTC
You could use Time::Piece and Time::Seconds which are core modules in recent Perl versions. `$ perl -MTime::Piece -MTime::Seconds -Mstrict -Mwarnings -E ' my $dateStr = q{2016-05-16 10:51:07}; my $dateFmt = q{%Y-%m-%d %H:%M:%S}; my $tp = Time::Piece->strptime( $dateStr, $dateFmt ); $tp -= ONE_HOUR; say $tp->strftime( $dateFmt );' 2016-05-16 09:51:07 $` [download] I hope this is helpful. Cheers, JohnGG	[reply] [d/l]
Re: Date/Time Manipulation by hippo (Archbishop) on May 24, 2016 at 18:55 UTC
Looking for a simple (hopefully) way of subtracting one hour from date - time in a file. Simple, you say? `perl -pe 's/ (\d\d)/sprintf(" %2.2i",$1-1)/e;'` [download]	[reply] [d/l]
Re^2: Date/Time Manipulation by Anonymous Monk on May 25, 2016 at 14:01 UTC
Thank you hippo After surrounding that with variable definitions, file paths, file open/close and prints to a new file in a Perl script, I am a VERY HAPPY CAMPER. Not sure how it works; will explore that.	[reply]
Re^3: Date/Time Manipulation by RobertJ (Acolyte) on May 25, 2016 at 14:04 UTC
Forgot to log in, RobertJ. Again thanks.	[reply]
Re^4: Date/Time Manipulation by johngg (Canon) on May 25, 2016 at 15:20 UTC
Re^5: Date/Time Manipulation by hippo (Archbishop) on May 25, 2016 at 15:27 UTC
Re^4: Date/Time Manipulation by RobertJ (Acolyte) on May 25, 2016 at 18:36 UTC
Re^5: Date/Time Manipulation by haukex (Archbishop) on May 25, 2016 at 18:47 UTC
Some notes below your chosen depth have not been shown here
Re: Date/Time Manipulation by mhearse (Chaplain) on May 24, 2016 at 18:38 UTC
Convert the date times to epoch. Then subtract 3600. Then convert epoch back to date time.	[reply]
Re: Date/Time Manipulation by talexb (Chancellor) on May 24, 2016 at 19:50 UTC
It seems like you want to re-state the times in a time zone that's an hour earlier .. so one approach you could take would be to read the timestamps in, change the timezone to one that's an hour earlier, and output the result. However, that's just an educated guess. Good luck! Alex / talexb / Toronto Thanks PJ. We owe you so much. Groklaw -- RIP -- 2003 to 2013.	[reply]