Customers can choose between standard delivery options and Same Day delivery.
Same Day delivery option is only selectable when in between the time range.

Instalation guide:

- Upload the zip file by accessing Extensions > Installer section
- Go to Extensions > Extensions > Shipping Methods (from dropdown) > Sameday and click install
- After that, click edit next to our new extension and configure it
- Give user group permission to access our new extension by Systems > Users > Users Group
- Enjoy!

I have not tested the extension for other than specified opencart versions, however I would be happy to help anyone integrate it in an older/newer version.
Feel free to contact me!