As reported in several places, users have trouble getting the correct timestamp in their contact form emails:
My timezone is already set correctly as instructed here:
So I decided to look into the code.
It looks like the code just uses PHP's plain time() method to get the timestamp. This will always be in UTC. So I corrected it to current_time('timestamp') as according to the WordPress docs:
The changes must be made on lines 499 and 938 in file si-contact-form/includes/class-fscf-process.php . You can edit the plugin from within WordPress and just Ctrl+F (or Command+F) for time() and replace it.
Works great for me on WordPress 3.8.2 with FS Contact Form plugin 4.0.18.