I have several D-Link cameras, including 2 of this model. This one (including both of mine) is the only one that gets the time wrong. Sometimes rebooting partly fixes it, but not always. And as you noticed, sometimes some of the times (like the on-screen clock) are correct, but other times (like the time in the filenames) are incorrect. And, if you set up a schedule to enable motion detection, sometimes that happens on the wrong schedule too. It seems to have problems with time zones and daylight saving time. Very frustrating. This seems to be a firmware bug in this model, because none of my other model cameras do this.
I use manual daylight savings (instead of automatic), and this partly fixes it. Maybe if you set the time completely manually, so your time zone and GMT (UCT) are the same, with daylight saving time off, it might get the time right. I have not done this, because I like the auto sync to a time server.
What are you using for motion detection? Visual or PIR? Neither is perfect.