Sunday is of no particular significance in Judaism, it is just the first day of the week. In Israel, all the Western songs complaining about Monday don't make sense to the Israelis because the first day of the work week in Israel is Sunday.
The Jewish Sabbath, called 'Shabbat', is the 7th day of the week and starts Friday sundown and ends Saturday sundown.
Easter Sunday
For religious people Sunday can be very important
Because the majority of people in Spain are Christians and Easter Sunday is Christianity's most important day.
Mass is held every day of the week. Sunday is the most important day, which may be what you are asking about.
Although Saturday is the 'holy' day of the jews, in the early Church the first Jewish Christians began to worship on Sundays instead of the seventh day of the week (Saturday - the 'Sabbath') because it was on a Sunday that Jesus rose from death. This was considered such an important day that Sundays were chosen instead as a day of worship - a tradition that carries on to this day.
Sunday is the day of rest, when God finishe creating the world and rested. Moses gave the Jews commandments to the Jews and one of them was to keep the sabbath day holy (Sunday) this was very important to them and they took it very seriously. This has rubbed off on catholisism and so Catholics also believe that Sunday should be a day of rest (where you are one with god). This is a very old rule, and in this modern age churches have made acceptions for Saturday seeming as how important work and buisiness is these days.
The Jewish day of worship is Friday evening to Saturday evening. This is known as the Sabbath. Jews do perform the daily prayers on Sunday, just as they do on other weekdays. The longer services and holy day is the Sabbath.
Every week, pious Jews observe the Jewish holy day of Sabbath and follow its commandments and practices. The Sabbath begins at sunset on Friday and ends at sunset on Saturday.
Sunday is the day of rest in most western countries, it is a day of worship as Sunday is the Lord's day.
A holy day for rest and worship is Friday for the Muslims, Saturday for the Jews and Sunday for the Christians
It should actually be Saturday and not Sunday. Saturday is the Sabbath for Jews and some Christians, but Catholics and most major Protestant sects observe Sunday as the Sabbath, but Catholics may attend Saturday evening Mass , as the Jews observe from sundown Friday to sundown Saturday, Catholics now may attend Mass from Saturday thru Sunday.
Sunday is just the first day of the week for Jews. There's no religious significance to the day.