Okla. Stat. tit. 6, § 6-601: Business days and hours

A. 1. The days and hours within which a state bank or national

bank, credit union, savings association or trust company may be open

for business may be set by its board of directors.

2. Any plan so adopted by any such organization may be changed

by it from time to time in its discretion.

B. 1. Any act authorized, required or permitted to be

performed at or by any such bank, association or credit union on a

business day when such bank, association or credit union is so

closed may be performed on the next succeeding business day, and no

liability or loss of rights of any kind shall result from such

delay. If the organization chooses to close on a weekday which is

not a legal holiday, the bank shall still have responsibility for

paying or returning checks by its midnight deadline. For purposes

of this section, legal holidays and Saturday and Sunday shall not be

considered "business days".

2. In no case shall such bank, credit union, or savings

association be closed for more than three (3) consecutive days,

except as permitted under Section 603 of this title. Notice of a

change in hours or days of operation should be furnished to

customers to the extent practicable.