The show seems to switch from day to night frequently. One example is when Clarke, Finn and the others go to the meeting on the bridge on unity day. Finn comes and gets Clarke at night, by the time the reach the bridge it's daylight. Dawn you might think... until after their 5 minute conversation, when they're retreating, it's night again.
In the Unity Day celebrations, the Indian flag is upside down.
Bellamy tries to fire his assault rifle twice, but because of a dud round, it fails both times. There is an audible click each time he tries. The first attempt there would be a click, because the firing pin was charged when the last round was ejected. However, without that charge either automatically when a round is ejected or manually pulling the charging handle, the second attempt would have been silent since the firing pin was not engaged.
The grounder's leader Anya states that the missiles (flares) burned a village to the ground. If this were true, the flares couldn't have flown very far, otherwise that village would have been too far away for the grounders to know about. In a previous episode, when you saw the flares from space, it was obvious the flares traveled hundreds if not thousands of miles away.
When Clarke and Bellamy are looking up at the sky watching the drop ship entry, they are looking in noticeably different directions.