To deal with the dates, use my formula method and then use the A|B column to lookup the dates.
Suppose you have, in A2:C20
{1,"a",40913,"1|a";1,"a",40913,"1|b";1,"a",40944," 2|a";1,"a",40973,"2|c";1,"b",40943,"3|c";1,"b",409 43,"4|d";1,"b",40972,"";2,"a",40970,"";2,"a",40970 ,"";2,"a",41001,"";2,"c",41031,"";2,"c",41064,"";3 ,"c",41094,"";3,"c",41125,"";3,"c",41156,"";3,"c", 41186,"";4,"d",40971,"";4,"d",40971,"";4,"d",41002 ,""}
Then naming the result of my first formula C_
in E2 array enter and fill down
=IFERROR(INDEX(C_,MATCH(D2,A&"|"&B,)),"")
This produces the required dates
={40913;40943;40970;41031;41094;40971}
Let me know if you would like a workbook showing the example. The above may look dauting for you to interpret and construct in your workbook.
Regards
Brian