Bash date calculates time addition incorrectly

Question

I am writing a simple bash script for computing time and date by adding seconds onto a random date that I give. It worked fine so far but going from 2016-03-13 00:00:00 to 2016-03-13 03:00:00 skips 2016-03-13 02:00:00.

Verions of bash that I've tried are 4.4.23(1)-release and 5.3.8(1)-release, and they both gave me the same results.

The command below

date -d "2016-03-13 00:00:00 7199 seconds" +%Y-%m-%d-%H-%M-%S

gives

2016-03-13-01-59-59

which is correct. But with

date -d "2016-03-13 00:00:00 7200 seconds" +%Y-%m-%d-%H-%M-%S

I get

2016-03-13-03-00-00

which is supposed to be

2016-03-13-02-00-00

Am I missing something here?

You don't disable it. The computer is right and you're wrong. On that date 3am was two hours after midnight. — matt
– matt, Commented Dec 11 at 2:23
@Redshoe Yes, since UTC doesn't use DST TZ=UTC date -d "2016-03-13 00:00:00 7200 seconds" +%Y-%m-%d-%H-%M-%S should work — Ted Lyngmo
– Ted Lyngmo, Commented Dec 11 at 2:32
Voted to reopen (I noticed this was closed for not being reproducible - and it is about timezones - it is 100% reproducible given a DST timezone where the skip happens) — Ted Lyngmo
– Ted Lyngmo, Commented Dec 12 at 20:46

Ted Lyngmo · Accepted Answer · 2025-12-11 02:55:42Z

4

Since the UTC timezone doesn't use daylight savings time (which is what messes this up), this will work:

TZ=UTC date -d "2016-03-13 00:00:00 7200 seconds" +%Y-%m-%d-%H-%M-%S

answered Dec 11 at 2:55

Ted Lyngmo

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