From http://abstractspaces.wordpress.com/2009/05/02/common-date-time-formulas-for-sharepoint-calculated-fields/ for future reference:
Get Week of the year
=DATE(YEAR([Start Time]),MONTH([Start Time]),DAY([Start Time]))+0.5-WEEKDAY(DATE(YEAR([Start Time]),MONTH([Start Time]),DAY([Start Time])),2)+1
First day of the week for a given date:
=[Start Date]-WEEKDAY([Start Date])+1
Last day of the week for a given date:
=[End Date]+7-WEEKDAY([End Date])
First day of the month for a given date:
=DATEVALUE(“1/”&MONTH([Start Date])&”/”&YEAR([Start Date]))
Last day of the month for a given year (does not handle Feb 29). Result is in date format:
=DATEVALUE (CHOOSE(MONTH([End Date]),31,28,31,30,31,30,31,31,30,31,30,31) &”/” & MONTH([End Date])&”/”&YEAR([End Date]))
Day Name of the week : e.g Monday, Mon
=TEXT(WEEKDAY([Start Date]), “dddd”)
=TEXT(WEEKDAY([Start Date]), “ddd”)
The name of the month for a given date – numbered for sorting – e.g. 01. January:
=CHOOSE(MONTH([Date Created]),”01. January”, “02. February”, “03. March”, “04. April”, “05. May” , “06. June” , “07. July” , “08. August” , “09. September” , “10. October” , “11. November” , “12. December”)
Get Hours difference between two Date-Time :
=IF(NOT(ISBLANK([End Time])),([End Time]-[Start Time])*24,0)
Date Difference in days – Hours – Min format : e.g 4days 5hours 10min :
=YEAR(Today)-YEAR(Created)-IF(OR(MONTH(Today)<MONTH(Created),AND(MONTH(Today)=MONTH(Created),
DAY(Today)<DAY(Created))),1,0)&” years, “&MONTH(Today)-MONTH(Created)+IF(AND(MONTH(Today)
< =MONTH(Created),DAY(Today)<DAY(Created)),11,IF(AND(MONTH(Today)<MONTH(Created),DAY(Today)
> =DAY(Created)),12,IF(AND(MONTH(Today)>MONTH(Created),DAY(Today)<DAY(Created)),-1)))&” months,
“&Today-DATE(YEAR(Today),MONTH(Today)-IF(DAY(Today)<DAY(Created),1,0),DAY(Created))&” days”
