Sum of Time column


I am very new user to Knime tool. I am trying to use this tool to prepare pie chart on sum of time spent against each activity.

i am successfully able to read the data from excel, able to convert the column data to Datetime, going ahead i am trying to group by the module & take sum on the time spent column. But, i am not getting any option to create Sum on aggregration tabs.

I am wondering that is summation on time column not allowed in Knime or am i missing something?

Kindly guide me to get through this.

Thanking You,

Bhavin Shah.

First of all, a time variable as in the time types refer to the instance on a clock, and not the duration. That is why it doesn't make sense to aggregate it. 

Howevver, if you have duration periods stored in a time field, such as say 0:13:12 for 0 hour, 13 minutes and 12 seconds as opposed to 12 minutes and 13 seconds past midnight, then you can aggregate by first extracting the hour, minute and second using a Time Field Extractor node, then use a Group by to aggregate the resulting integer fields of hour, minute and second. You can then use a Math Formula node to produce a duration.