Rush hours follow work schedules everywhere, so the danger zones are roughly early-to-mid morning and late afternoon into early evening on weekdays. The exact windows shift by country depending on local working culture, and some places add a lunchtime bump. In the biggest metros of Asia and elsewhere, peak crowding can be intense, with staff literally helping pack trains, while smaller cities just feel busy.
Avoidance strategies are universal: travel mid-morning through early afternoon when you can, and note that the first stations on a line are your best chance of a seat. Friday evenings, the days before public holidays, and event nights are their own special chaos. Transit apps increasingly show real-time crowding levels, which is worth checking before you leave.
If you must commute at peak, small adjustments help more than you would expect. Shifting your trip by even half an hour often transforms the experience, and some employers accommodate staggered hours if you ask. Board at the ends of the platform where cars are usually emptier, have your ticket or card ready before the gates, and keep bags in front of you both for space and for security.