Last startup I worked for hired a Nepal-based QA person. There was a bunch of calendaring and daily/weekly charts in the apps, and she found bugs in _everything_.
I make sure to test with Nepal time whenever I'm testing date/time stuff now.
And, of course, there's the (hopefully apocryphal) story of the French initially referring to GMT as 'Paris time minus nine minutes and twenty-one seconds'.
As it happens, this story isn't apocryphal at all! One can readily find the original law, which was enacted on March 9, 1911, and published in the Journal officiel of March 10, 1911 [0]:
> Article unique. — L'heure légale en France et en Algérie est l'heure, temps moyen de Paris, retardée de neuf minutes vingt et une secondes.
The decree which finally replaced it was made on August 9, 1978, and published on August 19, 1978 [1]:
> Art. 2. — Sur l'ensemble du territoire de la République française, le temps légal (ou heure légale) est défini à partir du temps universel coordonné (UTC) établi par le bureau international de l'heure.
When I built a live clock for some new CasparCG based graphics for a major TV program out of singapore some years back, a colleague reviewing it in London tried to trick it with a Nepal offset — apparently they’d run into an issue with the Viz system they used in 2015 when there were a lot of lives from Nepal.
I make sure to test with Nepal time whenever I'm testing date/time stuff now.