Legislative actions, practices, customs, Treaties, and Conventions have standardized working hours as eight ( hours per day and five (5) days per week. The Treaty of Versailles of June 28, 1919, which officially established the International Labour Office, now known as The International Labour Organization (ILO), puts a peg of finality on work hours and affirmed eight hours work day and this was subsequently ratified by its 52 Nations.

Nigeria is a signatory to the International Labour Organization and by implication to its treaties and conventions. It is right to posit therefore that the official work hour in Nigeria is eight hour, five days a week.

However, it is important to note the following clauses in the Nigerian Labour Act 1990:
Section 13, subsection 1, which states that “Normal hours of work in any undertaking shall be those fixed:

1. by mutual agreement; or
2. by collective bargaining within the organization or industry concerned; or
3. by an industrial wages board …”

The implication of this pronouncement by the Act is that the responsibility for the determination of hours of work rests squarely on agreement between the employer and the employee (Contract or mutual agreement), or by collective bargaining (Employers Associations and Labour Unions or workers’ representatives) or an industrial wages board where there is no instrument for collective bargaining. . click the link to full article: http://www.askkayodemicah.com.ng/2017/11/18/overtime-work-bases-nigerian-labour-law-computation-mode-payment/