Why is February 28 in the Gregorian calendar

 The solar calendar tries to make the average number of days in a year equal to the length of the regression year 
	 However, the number of months and days in a year is artificially prescribed 
	
caesar（Gaius Julius Caesar） After the conquest of Egypt , Brought back the Gregorian calendar of Egypt 
	 because caesar My birthday is in 7 month , He asked that this month must be the big month 
	 Therefore, the celestial litterateurs set the single month as the big month 
		 Six months , Six months make an extra day in ordinary years , Only one day is deducted from a certain month 
		 At that time, the death penalty in Rome was 2 Month execution , People think this is an unlucky month 
		 therefore 2 The month is subtracted by one day , Only 29 God 
		
caesar After the death of , His heir Octavian （Gaius Octavius Thurinus） Succession 
	 Octavian's birthday is 8 month , He stipulated that 8 The month is set as the big month 
		 And from 8 After month , The double moon is the big moon 
	 thus , There are seven big months in a year 
	 Unlucky 2 Month minus another day , Only 28 God 

note:
	july
		julius caesar
	august
		emperor Augustus -> Gaius Octavius Thurinus