i want to generate random number using current date ?

We can't specifically answer that: it depends on how you are storing information.
If you are using a database, then there are one set of ways, if these are for filenames, then there is another - and so on.
Because you was a daily sequence number, you need to store either the previous value or a "date" and "sequence number" separately - and how you generate the "next" value depends on how your whole system is used. If this is a single user system, then it's a trivial task - but for a multiuser environment it's a lot more complex as you have to prevent two separate processes from generating the same value.

But some general rules apply anyway:
1) Never "Precalculate" the value: only ever assign it when you commit a record, or file or whatever. Do not try to say "my next number will be 'dddddnnnnn' so I'll use that" - it will always give you grief at some point
2) If in doubt, assume that you will be using this as multiuser. It's more complex, but a lot easier to implement and test to start with than to add later.
3) If possible, take advantages of facilities provided by the environment: databases are (relatively) used to this and can make things easier. So if you are using a database, don't rely on a "manual system" implemented electronically.