It is 9:47 PM on December 24th. The family is arriving and the turkey is in the oven when my phone buzzes.
"Production is showing wrong dates on all invoices generated today."
Of course it is. Production bugs don't take holidays.
I open my laptop "just for five minutes." My wife gives me The Look. You know The Look. The one that says "if you spend Christmas Eve debugging I will tell your mother what you ACTUALLY do for a living."
I check the logs. All invoices generated after 9 PM show December 25th instead of December 24th. The first customer questions start reaching support.
I suspect a timezone issue immediately. It is always a timezone issue.
Our server runs in UTC and Brasília is UTC-3. At 9 PM in Brasília it is already midnight UTC, December 25th. Our date formatting function was formatting the date in the server timezone (UTC) instead of America/Sao_Paulo, because I, six months earlier, wrote new Date() instead of using the timezone utility I had built myself.
The fix takes one line. I deploy it and verify before closing the laptop.
Total time: 22 minutes, with all five stages of grief. Denial: it can't be a timezone bug, we fixed those. Anger: why is time so hard? Bargaining: maybe I can just change the server clock. Depression: I am debugging on Christmas Eve. Acceptance: it's always a timezone issue.
The turkey survived, my wife forgave me, and the invoices have the correct dates.
Merry Christmas. May your dates always be timezone-aware.