You must have heard about it. Indian Railways is going in for a numbering scheme change. Effective 20th Dec, we will have the scheme change from 4 digit numbers to 5 digit numbers. Largely, it should be smooth, as the bulk of the trains – all Mails/Expresses/Rajdhanis/Shatabdis, will just have a prefix of 1 to the existing number. For example:
2833 (Howrah Express) becomes 12833
2493 (Rajdhani Express) becomes 12493
The special trains are supposed to have a prefix 0. But a check into the page set up by Indian Railways, doesn’t show this to be the case consistently. For example:
0233 (Hmh Jp Special) becomes 09733
0465(Dli Pnp Special) remains 0465
You can check for a train number change, on this page set up by Railways.
Update (on 21/Dec):
We moved to the new train numbers: Here is a full list of changes.