Oh and what is OPD on the tank? I'm new to gas tanks.
Overflow Protection Device.
Over simplified, it's the triangle shaped valve.
The date code is stamped on the collar (mm/yy) and you've got 12 years from then.
Most places I've been to, they don't even look at the date. This is where I state the 'if you blow yourself up don't blame me' disclaimer.
If it's a star shaped valve, don't bother filling. It's not protected.