hi Tom Clark, I just committed a new fix for the Visualizer to explictly use UTC time in the recharts chart data. Can you please check? This is a tricky bug that probably only occurs at certain times of day.

Yep, I still see it. I'm in NY and today's (Friday) timestamp is . I lifted yesterday (Thursday) but the App thinks I lifted on Wednesday.

As I enter in strict dates there should be no timezone conversion necessary; ingest dates as UTC. If a cell has a timestamp you can assume it's a UTC timestamp and convert the local time to UTC by truncating the timezone.

Hmm but it might not with inputs late at night, if they fly to a new timezone, or if they change computers. It gets even more complicated if someone has a mix of timestamp, dates, and/or if you get the last_modified_at from Google itself.

Timezones are hard XD

This may have been a weird time zone error - I've implemented a possible fix. Let me know if it works. I can't reproduce your problem. See also if you only have the problem in the morning or evening, that would indicate a time zone error...

Oh that's not good at all. Thanks for reporting - I don't have that with my data, but that's why getting user feedback is so good. I'll have to take a closer look at your spreadsheet which you have already given me the link for.