Traditional Culture Encyclopedia - Almanac inquiry - Why doesn't Apple's mobile phone display the holiday time in Gregorian calendar?

Why doesn't Apple's mobile phone display the holiday time in Gregorian calendar?

Set the date and time for iPhone: Choose General Date and Time, and then turn off automatic setting. Tap Time Zone, and then enter the name of the major city in your time zone. Tap the date and time back button, tap Set Date and Time, and then enter the date and time.