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I will not ask why a timestamp is 1 January 1970 at 00:00 but in several cases in my computer they are 1 January 1970 at 01:00, how did the 01:00 coincidentally get set with a number of apps? enter image description here

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The Empty String Photographer
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Niklas Rosencrantz
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    The 01:00 is unlikely to be set but shown to you due to your local timezone setting. – Paul Pazderski Jul 30 '23 at 14:29
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    Timezone? `echo "$TZ"`. – waltinator Jul 30 '23 at 14:30
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    Oh I'd expect the epoch time to be midnight local time fore Bell Labs. So if the government in Bourdara removes 14 days from the calendar then epoch time would be not 1 January even...? – Niklas Rosencrantz Jul 31 '23 at 06:02
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    Re "*I'd expect the epoch time to be midnight local time fore Bell Labs*", It's 1970-01-01T00:00:00Z, the "Z" meaning UTC – ikegami Jul 31 '23 at 16:34
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    Re "*So if the government in Bourdara removes 14 days from the calendar*", Then they wouldn't be following the Gregorian calendar like basically the rest of the world, and you have have to figure out how to translate 1970-01-01 into their calendar. Exactly how you have to translate 00:00:00Z into your local time zone if you want to know what the epoch was in your time zone. – ikegami Jul 31 '23 at 16:58
  • Bourdara would create an absolutely confusing situation because their calendar is 14 days away from everyone else. Since the output comes from a Mac, they would have to convince Apple to support their timezone which is 14 x 24 + 1 hour away from everyone else in MacOS (and iOS probably), and Apple would likely tell them to go away. Only less polite. – gnasher729 Aug 02 '23 at 14:21

1 Answers1

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The UK government (in its infinite wisdom) decided to experiment with Daylight Saving Time.

It shifted to DST on Sunday, 18 February, 1968, and omitted the shift back that Autumn.

It observed DST all through 1969 and 1970, did nothing in the Spring of 1971, and shifted back to GMT on Sunday, 31 October, 1971.

Therefore, the Unix base time of 0 is correctly shown as 01:00:00 for the UK timezone.

See https://www.timeanddate.com/time/change/uk/london?year=1970

$ date -d @0
Thu  1 Jan 01:00:00 BST 1970
Paul_Pedant
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    I got indirectly caught by this one myself, several years ago — took me ages to track down, as it's so counterintuitive! (British _Summer_ Time, in January???) (BTW, the term ‘daylight saving time’ isn't used in the UK.) – gidds Jul 31 '23 at 20:18
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    @gidds I have lived in the UK for 74 years, and I am still mildly surprised that UTC and GMT are the same (in spite of standing on the Prime Meridian at Greenwich). Agreed that BST is British Summer Time (although Summer itself is elusive). But New York has Eastern Time (EST/EDT Standard and Daylight). I understand DST to be the generic term for any seasonal adjustment to local wall clock time. I am also pleased that most of India runs at UTC+5:30, and delighted that Assam uses "Tea Garden Time" at UTC+6:30. – Paul_Pedant Jul 31 '23 at 22:51
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    Epoch time 0 (`1970-01-01Z00:00:00`) was also at `1970-01-01T01:00:00` in many European countries (France, Germany, Poland, Italy...) as they were and still are UTC+01:00 in Winter. – Stéphane Chazelas Aug 01 '23 at 09:16
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    [ksh93 actually gets the time wrong for epoch 0 in the Europe/London timezone](https://github.com/att/ast/issues/17) – Stéphane Chazelas Aug 01 '23 at 09:24
  • @Paul_Pedant _all_ of India officially runs on UTC+5:30. Assam has been campaigning for a split timezone for decades now, but it's still not recognized by the central government. – muru Aug 01 '23 at 23:26
  • @Paul_Pedant There _is_ no generic term, just like there’s no generic term for the part of a car that you keep luggage in. It’s referred to as daylight saving time in US English and as summer time in UK English. – Mike Scott Aug 02 '23 at 04:14
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    @MikeScott I refer you to Wikipedia articles "Daylight saving time" and "Daylight saving time by country". Even in the USA, DST is a generic term: there are nine US time zones (4 for the 48 states, 3 for territories, plus Alaska and Hawaii). Each has its own acronym (e.g. MDT is Mountain Daylight Time), so DST means nine different offsets from UTC in the US alone. It is not summer time in the UK: it is BST -- British Summer Time. – Paul_Pedant Aug 02 '23 at 07:38
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    @Paul_Pedant BST is the specific instance in the UK, summer time is the generic term. For example, in the UK we say that the US is currently on summer time. – Mike Scott Aug 02 '23 at 07:53
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    @MikeScott In rural Wiltshire, "summer time" is the week when you take the bus to Weston-Super-Mare to sit in a bus shelter on the promenade eating a bacon bap, and watching the rain coming in off the Brecon Beacons while the paddle steamer Waverley goes aground on the sandbank. The other 51 weeks of the year, we technical types prefer to be slightly more specific. – Paul_Pedant Aug 02 '23 at 09:09
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    @Paul_Pedant in Lancashire we can tell it's summer because the rain gets warmer. – SusanW Aug 02 '23 at 11:13
  • Apple is quite good at keeping track of historical times. That has led to bug reports where Apple answered "no, it's correct, it's not our software that's messed up, it's your calendar". – gnasher729 Aug 02 '23 at 14:25