Tahajjud & prayer-day times
The whole prayer day on one timeline: the last third of the night, midnight, the Duha window, and the three times voluntary prayer is avoided.
Choose a location to begin
You will see tonight’s last third, midnight, and the day’s windows in the location’s time zone.
How these times are worked out
The night is measured from sunset to the next morning’s Fajr, the way most scholars measure it for the end of Isha and for the last third. Midnight is its halfway point, and the last third begins two thirds of the way through. Prayer times come from AlAdhan; the night is divided here.
The margins around sunrise, the meridian, and sunset are common conventions (15, 10, and 15 minutes). Scholars differ on their exact length; follow your local mosque when it publishes its own.
Hadith references: Sahih al-Bukhari 1145 · Sahih Muslim 831 · Sahih al-Bukhari 586 · Sahih Muslim 748 · Sahih Muslim 612. AlAdhan.
Questions
When is the last third of the night?
Divide the time between Maghrib and the next Fajr into three. The last third begins after two of those parts have passed. If Maghrib is at 7:00 pm and Fajr at 5:00 am, the night is 10 hours, so the last third begins at about 11:40 pm.
When is Islamic midnight?
Halfway between Maghrib and Fajr. It is not 12:00 am. It marks the end of the preferred time for Isha.
What are the times when voluntary prayer is avoided?
While the sun rises until it is fully up, while it is at its height at midday, and while it sets, together with the time after the Fajr and Asr prayers. Missed obligatory prayers may still be made up.