THE 1 HOUR PER YEAR BUG (BUT ONLY IN PACIFIC TIME!)

Summary from the TLDR Web Dev newsletter

Google Docs encountered a peculiar bug in 2021. Users in the Pacific Time Zone reported seeing timestamps for new comments and replies in Docs that were displayed as being created "tomorrow", despite being created the previous day. The cause was traced to an error in the date formatting logic used by Google Docs, which incorrectly calculated the number of hours between the current time and a past time due to the change in time zone offset caused by daylight saving time. This bug only affected users in the Pacific Time Zone during the single hour when daylight saving time transitioned.