Values for interval in SQL Server DateDiff functions

Today, in the work of a problem, statistics this week, the use of the DateDiff function due to the confusion of W and week produce statistical results error

The setting values for the parameter interval are as follows:

Value	Abbreviation (SQL Server)	Description
Year	Yy	Year 1753 ~ 9999
Quarter	Qq	Season 1 ~ 4
Month	MM or M	Month 1 ~ 12
Day of the Year	Dy or D	The number of days in a year, the day of the year 1-366
Day	Dd	Day, 1-31
Weekday	DW or W	The number of days in a week, the day of the week 1-7
Week	Wk	Week, week of the year 0 ~ 51
Hour	Hh	Time 0 ~ 23
Minute	Mi	Minutes 0 ~ 59
Second	Ss	seconds 0 ~ 59
millisecond	ms	milliseconds 0 ~ 999