I encountered a strange issue while updating water logs using a third‑party application. After some testing, I was able to narrow it down to the REST API: the entries are being shifted to the previous date.
These are the REST actions with results in the next line, which I sent. I removed the headers for readability and security.
GET "https://api.fitbit.com/1/user/-/foods/log/water/date/#date2#.json
{"summary":{"water":0},"water":[]}
GET "https://api.fitbit.com/1/user/-/foods/log/water/date/#date1#.json"
{"summary":{"water":0},"water":[]}
POST "https://api.fitbit.com/1/user/-/foods/log/water.json?date=#date2#&amount=333&unit=ml
{"waterLog":{"amount":333,"logId":10902129983}}
GET https://api.fitbit.com/1/user/-/foods/log/water/date/#date2#.json
{"summary":{"water":333},"water":[{"amount":333,"logId":10902129983}]}
GET "https://api.fitbit.com/1/user/-/foods/log/water/date/#date1#.json
{"summary":{"water":0},"water":[]}
POST "https://api.fitbit.com/1/user/-/foods/log/water/10902129983.json?amount=222.0&unit=ml
{"waterLog":{"amount":222,"logId":10902129983}}
GET "https://api.fitbit.com/1/user/-/foods/log/water/date/#date2#.json
{"summary":{"water":0},"water":[]}
GET "https://api.fitbit.com/1/user/-/foods/log/water/date/#date1#.json
{"summary":{"water":222},"water":[{"amount":222,"logId":10902129983}]}
For context: I am located in CET (UTC+1), and the current local time here is 23:27, when I tried the actions.
#date1# and #date2# are actual dates formatted as yyyy-MM-dd, but I was not allowed to post the real values.
#date1# = 01 March 2026
#date2# = 02 March 2026
Please look into this issue and fix it.
Kind regards.
