End time can be before start time

[amythetester]

User is able to enter an earlier end time than the start time

[mmcknett]

Good find. End time before start time should show a validation error and inhibit the submit button.

I don't think there would be any good reason to preserve this behavior. If for some reason users need a "negative time span" feature, it should probably be thought about independently with a different storage mechanism. Any other strange date-related corner cases, such as logging at 1:30am on "fall back" day or logging an event that crossed time-zones, would be better handled by handling time zones explicitly.