Hi Thodoris:
Generally we can use time format for degrees since (not by chance) thee are
60 mins in 1 hour and in 1 degree of arc)
The problem is the decimal point where a colon is needed (7:28 not 7.28)
1) Use Edit | Find and Replace to convert dot to colon;
then put 60 in a blank cell, copy this, select you range of times, use
Edit|Paste Special Divide; format cells with m:ss
or
2) use a new column with (assuming first time is in A2) formula
=TIME(0,INT(A2),MOD(A2,1)*100) and format with mm:ss
or
3) use
=TIME(0,SUM(INT(A2:A4))+INT(SUM(MOD(A2:A4,1)*100)/60),MOD((SUM(MOD(A2:A4,1)*100)/60),1)*60)
entered as array formula with SHIFT+CTRL+ENTER
best wishes
