I replaced my iPad today but still warranty is not extended

See this support article:--> Your Hardware Warranty

For any further questions about this matter, please contact the Apple Store where you had your device replaced, or contact Apple Support directly, using this link:--> Get Support

Regards

Giulio

If your device is replaced under warranty - your original warranty continues to be valid for the replacement device. The warranty period may vary by geographic region or country - but will be calculated from the original date of purchase. If originally purchased within any EU member state, you will have a two-year warranty.

Unless your original device purchase was refunded - and you purchased a replacement device - the warranty date will not reset.

A replacement device provided by Apple as an exchange will usually have at least a 90-day warranty; as such, your revised warranty date will be 90-days or the balance of your original warranty - whichever is longer.