Salaam,
Praying is the first pillar of Islam and because of this there are some relaxation in it.
Islam does not force anyone but teach them in very nice manner to do the Islamic things.
In different Islamic sects the time is different but that difference is must like 10 to 15 minutes except Jumma pray which is almost 30 min.
I have given full details for praying, when it's time start and when it's time end. You can adjust your praying time in the light of below details and it will still be considered "right" and performed.
Praying 5 times in a day: There are 5 times in day when you have to pray to Allah and this is mandatory.
- Fajar, 2 rakat
- Zuhar (Duhar), 4 rakat
- Asar, 4 rakat
- Magrib, 3 rakat
- Isha'a), 4 rakat
These does not include any nafal, sunnat etc.
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Sunni Sect
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Fajar:
Fajr daily prayer must be offered (with loud recitation of the quran)
is from the beginning of dawn to sunrise.
Zuhar:
Time begins: when Sun has exactly halfway between sunrise and sunset
(This is when the sun is at the highest point in the sky)
Time ends: At the time when the Asr prayer begins (afternoon prayer)
Maliki school: if someone prays zuhr 30 minutes before sunset, he is
considered to have prayed the prayer "on time".
Asar:
Time begins: The Maliki, Shafi`i, and Hanbali schools say it is at
the time when the length of any object's shadow equals the length of
the object itself plus the length of that object's shadow at noon.
Hanafi school: it begins when the length of any object's
shadow is twice the length of the object plus the length of that
object's shadow at noon
Time ends: Once the sun has completely set below the horizon. However,
it is frowned upon (and sinful in the Maliki school) to delay the
prayer without a legitimate excuse to the point of the day in which
the sun turns a pale red or orange color as it begins to set, though
it would still be considered to have been prayed on time.
Maghrib:
Time begins: When the sun has completely set beneath the horizon;
immediately after the Asr prayer period ends.
Time Ends: Maliki and Shafi'i schools of law, the prescribed prayer time ends as soon as
enough time for a person to purify him/herself and pray has passed.
After that, according to the Maliki school, the Period of Necessity
lasts until a little before dawn, i.e., the beginning of Fajr prayer.
Most other scholarly opinions hold that the time for Maghrib prayer
ends when the time for Isha'a salat begins.
Isha'a:
Time begins: According to the Hanafi school, Isha begins when
complete darkness has arrived and the white twilight in the sky has
disappeared.
Maliki and Shafi'i schools, the time begins when the red thread has
disappeared from the sky.
Time ends: At the beginning of dawn when the time for Fajr prayer
begins. However, it is frowned upon to delay the prayer without a
legitimate excuse past the first 1/3 of the night ("night" in Islamic
law means the time between the entrance of the Maghrib prayer and the
entrance of the Fajr prayer). According to an opinion in the Maliki
school, the prohibition is from delaying the prayer beyond 1/2 the
night, rather than just 1/3.
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Shia Sect
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Fajar:
Start Fajr daily prayer starting time is beginning of dawn till you see the
whitnes of morning (which is called Saher).
End Once Sun rays are visible you cannot pray it and after that you have to pray it as Qaza.
Zuhar (Duhar):
Start When Sun has exactly halfway between sunrise and sunset
(This is when the sun is at the highest point in the sky)
End When Sun is down, not fully but the redness is visible in sky (i don't know what
its name in English) After that you have to pray it as Qaza.
Asar:
Start You can pray it right after reciting Zuhar
End When Sun is down, not fully but the redness is visible in sky. After that you have to pray it as
Qaza.
Maghrib:
Start You can pray it once Sun is fully down and the redness in sky is no
more visible
End You can still pray till mid night.
Isha'a:
Start You can pray it right after you recite Maghrib
End You can still pray till mid night.
In Shia sect Zuhr can be followed by Asr once the midday prayer has been recited and sufficient time has passed, and Maghrib can be followed by Isha'a once the evening prayer has been recited and sufficient time has passed.
Despite the relatively long period in which valid prayers can be recited, it is considered important to recite the prayer as soon as the time begins. But if you have difficulties to offer pray then you can delay it until you can offer it.