Which hour to use?

[myfs_94240]

Dear Master,
I have a nephew, born in the year 1999, in the yin earth Day Heavenly stem. The timing of birth is 5:25 P.M. in Singapore. So, is he born in the hour of the Rooster or is he born in the hour of the Monkey?
I am confused in the hour because I know that in Singapore, there is an adjustment in the timing of 1 hour faster since 1st May 1982. I understand that without the adjustment of the timing in the 1 hour faster, my nephew will be born at 4:25 P.M. which is in the hour of the Monkey.
So, now being born at 5:25 P.M. which hour should I use?
Please advice. Thank you.
Oswin lee