Sunday is the weekly day of rest in the Christian world. Saturday is the weekly day of rest in the Jewish state of Israel, Muslim countries and among Jewish communities. But in Turkey with a predominantly Muslim population (99%), Sunday is the weekly day of rest. If you can speak of a rest day; a lot of shops are open and people are 'beeing' around. And Turks have to work, hard, so often on Sunday as well.
Ataturk introduced a 'Free Sunday' in 1935 among other social reforms:
The activities of religious sects were banned by law (1925);
Western calendar was introduced (1925);
International numeric system was introduced (1928);
The Metric system was introduced (1931);
The nicknames and personal titles were abolished (1934);
Religious attire was prohibited in public (1934);
According to this law, religious personalities, irrespective of the religious groups they belong to, were not to wear religious attire in public but only in their sanctuaries.
The surname law was introduced (1934);
The modern secular system of jurisprudence instead of religious law is integrated (1926);
The liberation of the women of Turkey by giving them political and social rights.
a) Rights brought with medeni kanun (1926);
b) Rights for women to be elected for the parliament (1926).
See here the friction with the Muslim world!