$ date -u; date; date +%s
Sun Sep 13 12:26:39 UTC 2020
Sun Sep 13 17:56:39 IST 2020
1599999999
$ date -u; date; date +%s
Sun Sep 13 12:26:40 UTC 2020
Sun Sep 13 17:56:40 IST 2020
1600000000
An important point worth noting from the POSIX.1-2008 specification:
"Coordinated Universal Time (UTC) includes leap seconds. However, in POSIX time (seconds since the Epoch), leap seconds are ignored (not applied) to provide an easy and compatible method of computing time differences. Broken-down POSIX time is therefore not necessarily UTC, despite its appearance."
By the way, in case you got curious like me to find out if this Hacker News story (the original post) was posted exactly at this time, the answer is, it was posted at Unix timestamp 1599999975. See https://hacker-news.firebaseio.com/v0/item/24460382.json for the details.
Reproduced as text below:
An important point worth noting from the POSIX.1-2008 specification:"Coordinated Universal Time (UTC) includes leap seconds. However, in POSIX time (seconds since the Epoch), leap seconds are ignored (not applied) to provide an easy and compatible method of computing time differences. Broken-down POSIX time is therefore not necessarily UTC, despite its appearance."
See https://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xbd... for more details on the above point.
By the way, in case you got curious like me to find out if this Hacker News story (the original post) was posted exactly at this time, the answer is, it was posted at Unix timestamp 1599999975. See https://hacker-news.firebaseio.com/v0/item/24460382.json for the details.