Select Query From Two Tables?

I have two tables a and b column names are id and date. Data type of date in a and b are different

table (a)

date id
10-DEC-01 2:08:39 PM 1
10-DEC-01 2:08:39 PM 2
10-JAN-02 10:10:22 PM 3
10-JAN-02 10:10:22 PM 4
10-JAN-02 10:10:22 PM 5

table (b)
date id
10-DEC-01 1
10-DEC-01 2

I need table b like this one

table (b)

date id
10-DEC-01 1
10-DEC-01 2
10-JAN-02 3
10-JAN-02 4
10-JAN-02 5