Well, such time-only-based detection is extremely scary thing. It means if, by some reason, clocks on my computer not in full sync, or if I get from somewhere a file with incorrect timestamp it can cause all sort of interesting issues and lack of ability to delete won't be the worst thing. You can loose all updates of that file because btsync will overwrite it every time with "more recent" version. From another hand, if synced clock is so important for normal functioning of BTSync, it shouldn't even run in such situations but show some warning about time mismatch. As an example of such approach - as far as I remember some of AWS APIs are time-sensitive (for instance SQS) and won't accept request from devices with +/-300sec time offset. UPD: ok, this is not as bad as I thought. Looks like btsync normally ignores such file "from the future". Just tried to make a file with +5mins timestamp and btsync completely ignored this one and didn't sync till I put a valid timestamp.