You're right! IRCTC booking for most trains opens 120 days before the journey date (excluding the journey date itself). Here's the breakdown of booking times:

• Regular Bookings: These bookings open for all classes and trains at 8:00 AM IST (Indian Standard Time) on the 120th day before the journey date.
• Tatkal Bookings: Tatkal is a special quota for last-minute bookings. These bookings open one day in advance from the departure of the train. There are specific time windows depending on the type of berth:AC Berths: Booking starts at 10:00 AM ISTNon-AC Berths: Booking starts at 11:00 AM IST

Important Note: The IRCTC website might undergo scheduled maintenance during late night hours, typically between 11:45 PM IST to 12:20 AM IST. So, booking functionality might be limited during that window.