We have found a work around for this issue and have submitted an updated version of Dive Log (1.4.1) to Apple for review. Hopefully it will be reviewed and released quickly. In the meantime, there is a relatively easy way to work around the issue using the current version of Dive Log (1.4).
The problem occurs when using Dive Log in a time zone that is different than the time zone where Apple's Headquarters are located (Cupertino, CA - US/Pacific). The time and date pickers will display times relative to the US/Pacific time zone. The time and/or date displayed in the text fields above the picker will be correct. To enter and store the correct time you simply need to move the picker until the correct time is shown in the text field above the picker wheels. The time offset will be constant (for example if you are in London and trying to set a time of 16:00 (4:00 PM) the picker will need to be set to 8:00 for the the text field to correctly display 16:00) based on your current offset to US/Pacific time. As long as the time you want is showing in the text field (circled in red below), then the correct time will be saved in the logbook.
Note that this is also true for dates under certain circumstances. In the case of dates, you may need to set the picker to a day earlier or later than your desired date (again, as long as the correct date is showing in the text field above the picker then the correct date will be stored in the logbook).
Here is an image taken from an iPhone running iOS 4.0 and Dive Log in Tokyo, Japan demonstrating this issue:
in this case the diver is trying to enter a time of 13:09 (1:09 PM) but they need to select a time of 21:09 on the picker in order to get the correct time set.
We sincerely apologize for any inconvenience that this problem causes. Ironically, we live and work in the same time zone as Cupertino, CA so we didn't experience this issues testing Dive Log on iOS 4 prior to it's release (we did find and fix a number of other issues related to iOS 4 in the 1.4 update to Dive Log). This particular issue was only discovered once our testers and users located in other areas of the world were able to install iOS 4. We are looking forward to a quick approval of the update to Dive Log to eliminate this issue.
Cheers,
Greg