According to Julie Neidlinger who compiled 10 different studies to learn social media trends, the best times to post on Facebook are 1–4 p.m. late into the week and on weekends.
Saturday and Sunday at 12–1 p.m.
Thursday and Friday at 1–4 p.m.
Wednesday at 3 p.m.
Twitter: Best time to tweet is between 12–3 p.m., with a peak best time at 5 p.m. During the workweek is the best, though some niches might have more active audiences on the weekend.
Wednesday at noon and 5–6 p.m.
Monday–Friday at 12–3 p.m. and 5 p.m.
Experiment with 2–3 a.m., 6–7 a.m., and 9–10 p.m.
LinkedIn: Midweek posting is optimal from 5–6 p.m.
Tuesday at 10–11 a.m.
Tuesday, Wednesday, and Thursday at 7:30–8:30 a.m., 12 p.m., and 5–6 p.m.
Instagram: Instagram audiences are engaged throughout the week. Mondays should maybe get a little more attention.
Monday and Thursday at any time other than 3–4 p.m.
Videos any day at 9 p.m.–8 a.m.
Experiment with 2 a.m., 5 p.m., and Wednesday at 7 p.m.