Tool for cutting video
You can use ffmpeg, a command-line tool to do this.

If you want equal-sized splits, use 

ffmpeg -i input -segment_time 30 -f segment -force_key_frames expr:gte(t,n_forced*30) -reset_timestamps 1 a%02d.mp4


If you need to split at irregular intervals, use

ffmpeg -i input -crf 18 -segment_times 30,60,90 -f segment -force_key_frames 30,60,90 -reset_timestamps 1 files%01d.mp4