Any period during which the worker is working at the employer's disposal and carrying out his/her activity or duties, in accordance with national laws and/or practice. The International Labour Conference has adopted 25 Conventions and 14 non-binding Recommendations in the area of working time, beginning with its first Convention in 1919. These standards cover a range of subject-matter including hours of work, night work, weekly rest, paid leave, part-time work and workers with family responsibilities. The Hours of Work (Industry) Convention, 1919 (No. 1), introduced the standard of an eight-hour day and 48-hour week, which was later extended to workers in commerce and offices by the Hours of Work (Commerce and offices) Convention, 1930 (No. 30). The Forty-Hour Week Convention, 1935 (No. 47), advocates the principle of a 40-hour week, a principle further developed in the Reduction of Hours of Work Recommendation, 1962 (No. 116), which affirms the 40-hour week as a social standard to be reached progressively. The right to a minimum period of weekly rest was established for industrial workers in the Weekly Rest (Industry) Convention, 1921 (No. 18), and later extended to workers in commerce and offices by the Weekly Rest (Commerce and offices) Convention, 1957 (No. 103). Both of these instruments fix a minimum of 24 hours of uninterrupted rest every seven days, although the Weekly Rest (Commerce and offices) Recommendation, 1957 (No. 106), suggests a 36-hour rest period. Paid annual holidays became the subject of international standards in 1936 with the adoption of the Holidays with Pay Convention (No. 47). It sets a minimum entitlement of six days paid annual holiday for one year of service, later improved upon in the Holidays with Pay Convention (Revised), 1970 (No. 1329, which provides for a minimum annual holiday of three weeks. In more recent years, the Workers with Family Responsibilities Recommendation, 1981 (No. 165), suggests a progressive reduction of hours of work and the introduction of more flexible working time arrangements for workers with families; the Night Work Convention, 1990 (No. 171), incorporates a range of protective measures for night workers; and the Part-Time Work Convention, 1994 (No. 175), provides for the equitable treatment of part-time workers. See: Working time (organization of); Working time in the maritime sector (ships using Community ports); Working time of seafarers