After an upload of a local log the log date at the geocaching.com website differs in some hours. The reason is the timezone of your local log date differs from the timezone of the geocaching.com Servers. The Servers are located in Seattle USA (UTC-7).
The cache logs on the website are shown only with the date not the time. But if you are located in e.g. europe and you write your log early in the morning, the hour offset (e.g. Germany UTC+1 to USA UTC-7, difference 8 hours) will result in a day before on the website.
This is not nice but the API of geocaching.com gets the log date converted to UTC as required.
In a next version you can set an optional offset for the hours, which will be added before the upload to geocaching.com. You decide if the date at geocaching.com is shown correct or the date in other apps is correct.