DateDiff Errors

[swaxman]

I am pretty new to PowerBI

I am trying to do a DateDiff between two tables (OnboardingExcel which has unique records and TroubleTicket which has multiple records related to one ONboardingExcel record).  I have poked around on the forums and amelessly tried a couple solutions, but keep running into errors.

DATEDIFF('OnboardingExcel'[StartDate],'TroubleTicket'[Created_Date],DAY)

Error: A single value for column 'Created_Date' in table 'TroubleTicket' cannot be determined...

Days Past Start = IF(SUM(OnboardingExcel[StartDate])>SUM(TroubleTicket[Created_Date]),
DATEDIFF(SUM(TroubleTicket[Created_Date]),SUM(OnboardingExcel[StartDate]),DAY)*0,
DATEDIFF(SUM('OnboardingExcel'[StartDate]),SUM('TroubleTicket'[Created_Date]),DAY))

Error:Getting An invalid numeric representation of a date value was encountered.

Help is greatly appreciated!

[v-caliao-msft]

@swaxman,

Please try the DAX below.
Days Past Start = 1*(SUM(TroubleTicket[Created_Date])-SUM(OnboardingExcel[StartDate]))

Regards,

Charlie Liao

[swaxman]

I get a massive number 88309227309 and it is the same for every row.