Hi Sanjeev!
I provided:
=IF(ISBLANK(A1),"",TODAY())
If you put this in B1 it should work OK. However, you should "read"
the formula in that case as referring to the contents of the cell 1
cell to the left. If you copy the formula from B1 to (say) E7, the
reference will be changed to D7 (ie. one cell immediately to the left
of E7).
If you always want the formula to refer to column A then you must edit
it to:
=IF(ISBLANK($A1),"",TODAY())
Similarly if you want the formula to refer to row 1 then you must edit
it to:
=IF(ISBLANK(A$1),"",TODAY())
And if you want the formula to always refer to cell A1 wherever you
copy it to from B1 you must amend to:
=IF(ISBLANK($A$1),"",TODAY())
Be aware that tomorrow the function TODAY() will return a new date. If
you want it to be fixed at today's date, then refer to the link that
Frank has provided:
http://www.mcgimpsey.com/excel/timestamp.html