if i am purchses on 9th aprl and i am eneterd the bill on 5th april is this affact my itc

not really
coz you are filing the monthly return on 20th of may which include full month details

as per law that should not happen
when you purchase on 9th, you should have some evidance should have been existed on 5th April
example - agreement, pro-form, conformation,

what you are going to loose if you enter the same on 9th April, I believe nothing

can you please tell us the reason for predated entries

As per monthly return in 3B its not going to matter in claiming ITC , but as per Section 16 of CGST Act , ITC shall be available when you have received the bill & Goods .

Before completion of supplies bill recording is wrong practice or approach in your system. Please change