The Midnight Problem: Why Your Streak Looked Broken

TL;DR: We fixed a bug where users in different timezones saw incorrect "streak at risk" warnings.

What went wrong?

Our habit tracker shows a warning when you might lose your streak. The logic is simple: if you had a streak yesterday but didn't complete your habit, we warn you today.

The problem? We calculated "today" and "yesterday" using the server's clock, not yours.

# The bug
today = date.today()  # Server time (UTC)

If our server runs in UTC and you live in Los Angeles (UTC-8), here's what happens at 11pm your time:

• Your perspective: It's still Monday evening. You have time to complete your habit.
• Server perspective: It's 7am Tuesday. Monday is "yesterday." You missed it!

Result: False "streak at risk" warnings.

The fix

We now read your timezone from your profile and calculate dates accordingly:

# The fix
user_tz = ZoneInfo(profile.timezone or "UTC")
now_local = datetime.now(timezone.utc).astimezone(user_tz)
today = now_local.date()

Three steps:

1. Get your timezone setting (e.g., "America/Los_Angeles")
2. Convert current UTC time to your local time
3. Extract the date from that local time

Now "today" means today for you.

Lessons learned

• Always store timestamps in UTC
• Always convert to user's timezone for display and logic
• Time bugs are sneaky—they only appear for users far from your server's timezone

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This fix is available now. Make sure your timezone is set correctly in your profile settings!