On an individual level, Muslims are obligated to perform five prayers (salat) daily, and these are distributed throughout the day. Islamic prayer times were traditionally timed according to the changes in the movement of the sun, therefore their appointed times vary from day to day and from location to location. They occur before dawn (fajr), in the mid-afternoon (dhuhr), late afternoon (asr), sunset (maghrib), and evening (ishaa). The sun has nothing to do with the prayers aside from the issue of timing: this way, the five prayers are distributed throughout the day and night.
Individual prayers can be performed anywhere, including in a public place or a person's home. What makes the time of a prayer sacred is not where it is performed, but the fact that it corresponds to one of the appointed five times. Performing prayers at a prescribed time has the additional dimension of stepping away from one's mundane activities into a ritual performance, into a "time out of time" that is only valid for that prescribed prayer. One could not, for example, perform the mid-afternoon prayer at dawn. Nor is it advisable for a person to pray all the five prayers at once (though in case of long-distance travel, it is permitted according to the Sunni schools to combine some of the prayers for expedience and ease). Timing is therefore an essential element of these five prayers. Other free-form prayers or supplications, called duaa, are considered less formal since they are not required, though they are still sacred.
There are several accompanying factors that contribute to the sacredness of prayer time, namely ablution, behavior during prayer, and dress. To enter into ritual prayer, a Muslim first performs ablution, or a ritual washing. The Sunni schools of law have differing views on the details of ablution based on their view of what the proper custom (sunna) of Muhammad was. In general, all agree that pray-ers must wash their faces, hands, and lower arms, and wipe their feet. Among certain Sunni schools there is also a rinsing of the mouth and a wiping of the upper forehead and hairline. All agree that this ablution is required, and must be redone if the state of ritual purity is broken, which is usually effected by bodily functions. As such, five daily prayers likewise mean repeated ablutions. This is why most mosques include fountains or special washrooms specifically for ritual ablution before congregational prayers.
In addition to signaling the time for prayer with ablution, once one has entered into prayer, behavior signals that this time is sacred. When praying salat, a person does not speak to or interact with others, but focuses only on the prayer at hand. One may not eat or drink while praying, either. In addition, the ritual prayer calls for certain ritual garb. Namely, men and women in ritual prayer must wear garments that conceal their bodies. Women also cover their hair while praying, even if they do not for the rest of the day. In this sense, the preparation for, conduct during, and clothing for prayer signal that the five prayers take place in sacred time.
On the level of community, major holidays, such as the festival at the end of Ramadan or the Hajj to Mecca, occur at particular times of year in the Islamic calendar, though since the Islamic Calendar is lunar, the exact dates are unfixed. In addition to major events on the Muslim calendar, such as Hajj and Ramadan, it is important to remember that any of the five daily prayers may be conducted in a group as well as individually. Whether in a mosque or some other place, a group of people praying together is considered highly meritorious in Islam. One person, an imam, leads congregational prayers and the rest of the group follows this person in prayer. Though any prayer may be said in a congregational setting, the only time it is obligatory for Muslim men to attend a congregational prayer is the Friday mid-afternoon prayer. This is when a sermon (khutba) is read, and the prayer is performed communally.