fromdate produces an Epoch timestamp that is one hour off

[sgp]

Describe the bug

Parsing an ISO8601 timestamp yields a timestamp that is off by 3600 seconds.

To Reproduce

echo 1665511200 | jq todate | jq fromdate
1665514800

Expected behavior

Expected the round trip from todate (which produces an ISO8601) to fromdate would yield the same result.

Environment (please complete the following information):

• OS and Version: macOS Monterey 12.6, also reproduced on Linux (Fedora 34)
• jq version 1.6

Additional context

🤷

[mkj-pendo]

This is possibly related to DST.

On Fedora 36, jq 1.6:

$ date
Wed Oct 12 10:30:23 AM EDT 2022
$ echo 1665511200 | jq todate | jq fromdate
1665514800
$ export TZ=UTC
$ date
Wed Oct 12 02:31:08 PM UTC 2022
$ echo 1665511200 | jq todate | jq fromdate
1665511200

[sgp]

This is definitely mktime's fault, as fromdate is just an alias for strptime("%Y-%m-%dT%H:%M:%SZ")|mktime.

echo 1665511200 | jq -c 'todate|strptime("%Y-%m-%dT%H:%M:%SZ")'
[2022,9,11,18,0,0,2,283]

echo "[2022,9,11,18,0,0,2,283]" | jq mktime
1665514800

[sgp]

@mkj-pendo that checks out, as the code for mktime ... is messy.

[jmoldow]

I believe this is a duplicate of #2001 and can probably be closed, since it is fixed in jq 1.7 (though that version still isn't released to Debian and probably other systems as well).

[wader]

@jmoldow thanks for researching. @sgp are you able to reproduce with 1.7?

[sgp]

Tried this on jq 1.7.1, and it looks good

❯ echo "[2022,9,11,18,0,0,2,283]" | jq mktime
1665511200
❯ echo 1665511200 | jq -c 'todate|strptime("%Y-%m-%dT%H:%M:%SZ")'
[2022,9,11,18,0,0,2,283]
❯ echo 1665511200 | jq todate | jq fromdate

1665511200