I usually eat dinner AT 5pm. We use preposition AT for time ( e.g. at 4:30, at 19 o'clock) Preposition ON is used when we speak about days of the week (on Monday) And preposition IN is used for seasons ( in Spring), years ( in 1956) I hope this helps.

IN use it with >> Months or Seasons ( e.g. in May or in Winter) ON use it with >> days of week (e.g. On Saturday elc) AT use it with >> describe time ( at 9 o'clock ) So , you should use here AT not IN

1) I usually eat dinner at 5pm 'at' in this sentance normally means you start eating dinner when it becomes 5pm - if you used 'in' you would be taking about the time it takes to eat dinner. Example: I noramlly eat dinner in 5 minutes. 2) It is 3pm in Beijing, China. This sentance is perfectly fine.