Hi yordan
I tried for Char4 but i didn't get it. . .Just try by changing it to Char5.
write the below code in the getter method of the attribute
data : val1 type char2,
val2 type char5.
val1 = sy-uzeit+0(2).
val2 = sy-uzeit+2(2).
concatenate val1 val2 into val2 separated by ':'.
value = val2. "value returning parameter of getter method