Two Table columns of Date and Time you can merge as Timestamp using Timestamp function in DB2.
DB2 Function to Merge Date and Time
TIMESTAMP with a DATE column and a TIME column as arguments, Assume that table TABLEX contains a DATE column named DATECOL and a TIME column named TIMECOL.
For some row in the table, assume that DATECOL represents 25 December 2008 and TIMECOL represents 17 hours, 12 minutes, and 30 seconds after midnight.
The following function returns the value ‘2008-12-25-17.12.30.000000’.