Obtain the first and last days in SQL Server.

The first and last days of a known year are obtained in the project. I think the network is good and I will leave it as a backup.
1. The first day of a month

Select dateadd (mm, datediff (mm, 0, getdate (), 0)

2. Monday of the week

Select dateadd (wk, datediff (wk, 0, getdate (), 0)

3. The first day of the year
Select dateadd (YY, datediff (YY, 0, getdate (), 0)

4. The first day of the quarter

Select dateadd (QQ, datediff (QQ, 0, getdate (), 0)

5. midnight of the day

Select dateadd (DD, datediff (DD, 0, getdate (), 0)

6. Last day of last month

Select dateadd (MS,-3, dateadd (mm, datediff (mm, 0, getdate (), 0 ))

7. Last day of last year

Select dateadd (MS,-3, dateadd (YY, datediff (YY, 0, getdate (), 0 ))

8. Last day of the month

Select dateadd (MS,-3, dateadd (mm, datediff (M, 0, getdate () + 1, 0 ))

9. The last day of the year

Select dateadd (MS,-3, dateadd (YY, datediff (YY, 0, getdate () + 1, 0 ))

10. the first Monday of this month

Select dateadd (wk, datediff (wk, 0, dateadd (DD, 6-datepart (day, getdate (), getdate (), 0)