To blend two data sources you should have at least one common field in both the sources. That field will be your blending key.
Data type of the field should be same. As you said you wants to blend data source 1 with data source 2 where you have Minute field in DS1 and Start and End Date in DS2. Both the sources are belongs to Datetime attribute. BUT units of the fields are not same one is minutes and second is date. Using datediff() convert Start and End Date in minutes. So that you can blend with primary data source (minute field). Go to Data menu> edit relations and use custom to add the joining conditions.
I've tried to create a sample workbook as per your data structure. Have a look.
To blend I've create a calc field to get minute from Start and End date using Datediff().
Workbook (version 9.2) attached for your reference. Feel free to ask If you've any question. I dont know how much this help though you can get some Idea.
Data Blend - sample.twbx 12.7 KB
I should have stated that my Minutes field was also a datetime. With all fields being datetime format, I was trying to join two data sources with no other fields other than timestamp A is between timestamp B and timestamp C.
No worries, I think I may have found another way to display the data that will work for me. Thank you for your time.