As a pilot who has now and then made an utter fool of himself, I will share a way of remembering that conversion of UTC or Zulu time to local time is 4 hours in the summer and 5 hours in the winter (at least for the eastern time zone in North America).
"The hour change is short when the days are long, and long when the days are short."
That is, it's 5 hours (longer) when days are short (winter) and 4 hours (shorter) when days are long (summer.) This was told to me by a fellow pilot when I got it assbackwards one time. Rather than make fun of me, he told me this.
It really works great and I hope it helps you, too!