Saturday is the only day of the week in which the English name comes from Roman mythology. The English names of all of the other days of the week come from Anglo-Saxon polytheism. In India, Saturday is Shanivar, based on Shani, the Vedic God manifested in the planet Saturn. In the Thai solar calendar of Thailand, the day is named from the Pali word for Saturn, and the color associated with Saturday is purple. The Celtic languages also name this day for Saturn: Irish an Satharn or dia Sathuirn, Scottish Gaelic Disathairne, Welsh dydd Sadwrn, Breton disadorn.
In Jewish tradition Saturday is the Shabbat. Christianity adopted this tradition in terms of the Sabbath. Thus, in many languages the Saturday is named after the Sabbath. Eastern Orthodox churches distinguish between the Sabbath (Saturday) and the Lord's Day (Sunday). Roman Catholics put so little emphasis on that distinction that many among them follow – at least in colloquial language – the Protestant practice of calling Sunday the sabbath (see Sabbath in Christianity). Quakers traditionally refer to Saturday as "Seventh Day" eschewing the "pagan" origin of the name. In Islamic countries, Fridays are holidays, however they are considered as the sixth day of the week.
In the Eastern Orthodox Church Saturdays are days on which the Theotokos (Mother of God) and All Saints are commemorated, The day is also a general day of prayer for the dead, because it was on a Saturday that Jesus lay dead in the tomb. The Octoechos contains hyms on these themes, arranged in an eight-week cycle, that are chanted on Saturdays throughout the year. At the end of services on Saturday, the dismissal begins with the words: "May Christ our True God, through the intercessions of his most-pure Mother, of the holy, glorious and right victorious Martyrs, of our reverend and God-bearing Fathers…". For the Orthodox, Saturday is never a strict fast day. When a Saturday falls during one of the fasting seasons (Great Lent, Nativity Fast, Apostles' Fast, Dormition Fast) the fasting rules are always lessened to an extent. The Great Feast of the Exaltation of the Cross and the Beheading of St. John the Baptist are normally observed as strict fast days, but if they fall on a Saturday or Sunday, the fast is lessened.
In Scandinavian countries, Saturday is called Lördag or Löverdag etc., the name being derived from the old word laugr (hence Icelandic name Laugardagur), meaning bath, thus Lördag equates to bath-day. This is due to the Viking usage of bathing on Saturdays.
Today, Saturday is officially called Samstag in all German-speaking countries, however, there are two names for this day in modern Standard German. Samstag is always used in Austria, Liechtenstein, the German speaking part of Switzerland and generally used in southern and western Germany. It derives from Old High German sambaztac, which itself derives from Greek Σάββατο, and this Greek word derives from Hebrew שבת (Shabbat). However, the current German word for sabbath is Sabbat. The second name for Saturday in German is Sonnabend, which derives from Old High German sunnunaband, and is closely related to the Old English word sunnanæfen. It means literally "Sun eve", i.e. "The day before Sunday". Sonnabend is generally used in northern and eastern Germany, and was also the official name for Saturday in East Germany. In the Westphalian dialects of Low Saxon, in East Frisian Low Saxon and in the Saterland Frisian language, Saturday is called Satertag, also akin to Dutch Zaterdag, which has the same linguistic roots as the English word Saturday.
Similarly, the Romance languages follow the Greek usage, so that their word for "Saturday" is also a variation on "Sabbath": the Italian is sabato, the French is samedi, the Spanish and Portuguese is sábado and the Romanian is sâmbătă.
The Slavic languages regard Saturday as the sixth day of the week by naming Tuesday, Thursday, and Friday as the second, fourth, and fifth days of the week, although their name for Wednesday, middle, would imply that Saturday is the seventh day of the week. It is also interesting to note here that all Slavic languages derive their name for Saturday from Abrahamic tradition (e.g. Polish/Czech: sobota; Russian: суббота, subbota; Serbian/Ukrainian: субота, subota).
A similar numbering trend is also exhibited by the Baltic languages.
Beginning in the twentieth century, many Europeans have considered Saturday the sixth (penultimate) day of the week, and Sunday the last. This current European labour-oriented convention has been formalized by ISO 8601 which is used by businesses such as airlines in drawing up timetables, etc.