Source :

Step 1 :- Check existing installation date.

Step 1 :- First of all Open “Run” dialog box. To do so you can either do it by typing “Run” in the Start Menu search or by pressing the “Win+R” key combination.

Step 2 :- Now type “regedit” in the box that appears and hit enter. You can also type “regedit” in the Start Menu search to open Registry Editor.

Step 3 :- Navigate to “HKEY_LOCAL_MACHINE > SOFTWARE > Microsoft > Windows NT > CurrentVersion > “ in the Registry Editor Windows.

Step 4 :- You will find a key named “InstallDate” in the Right sidebar as shown in below image. Just Double Click on it.

Step 5 :- A new popup box will appear showing numerical value. This is the number of seconds between 1/1/1970 and your installation time.

Step 6 :- To change your Windows installation date just add or subtract the duration by which you want to change your date. For Example – If you wish to add one day to your installation date, then add “60x60x24=86400″ to the value.

If I wanted to add one day to my installation date, I would change the value to “1350224291″. Now Click OK after that.

Date Calculator