The code is definitely wrong. Without knowing what you have it is hard to know exactly which parts are wrong.
The variable DATE can either be a character string. In which case this line could work (depending on what values it has).
DateTime=input(Date, anydtdtm.);
Or it is a numeric variable in which case this line could work, as long as the number is the number of days and not the number of seconds that the statement above is trying to assign to the other variable DATETIME.
Month1 = intck('month', Date, '20Aug2020'd, 'continuous');
If DATE is a string and you want to convert it to a date value use the ANYDTDTE informat instead of the ANYDTDTM informat. If DATE is a number with a date value (number of days) and you want to create a datetime value then use the DHMS() function and supply the time of day you want to use, usually midnight is used.
DateTime = dhms(date,0,0,0);
If DATE is a number with a datetime value (number of seconds) and you want to count months you can either use the DTMONTH interval
Month1 = intck('dtmonth', Date, '20Aug2020:00:00:00'dt, 'continuous');
or convert it to a date value and use the MONTH interval.
Month1 = intck('month', datepart(Date), '20Aug2020'd, 'continuous');