How Is ` `Eid Determined?
Question

I have a question about the dates of the  `Eids...I know the  `Eid Al-Fitr is after the month of Ramadan and there is always dispute amongst this day (some will celebrate it on the 29th, while others celebrate it on the 30th), but in regards to the `Eid Al-Adha, does this day coincide with what the pilgrims are doing in Makkah, or can this day differ according to the different countries others are in?
Praise be to Allah.Is moon sighting binding for all countries?
The difference among the Muslims with regard to determining the first day of Ramadan and the time for  `Eid Al-Fitr stems from the differences of opinion among the jurists concerning the well-known issue, which is whether sighting of the new moon in one country becomes binding for all other countries, or should each country have its own sighting. This also applies to determining the date for `Eid Al-Adha. 
This is a matter that is subject to Ijtihad, and each group of scholars has produced its evidence, and both groups may even quote the same text as evidence. This has already been discussed in the answer to question no. 1248 . 
The view that sighting of the moon in one country becomes binding for all other countries is the view of the majority of scholars, and was the view favoured by Shaykh Ibn Baz (may Allah have mercy on him), as is stated in Majmu` Al-Fatawa (15/77). 
The view that there may be differences in sighting between different countries is the more correct view according to the Shafi`is, and was the view favoured by Shaykh Al-Islam Ibn Taymiyah, and by Shaykh Ibn `Uthaymin among contemporary scholars. We have quoted his fatwa in the answer to question no. 40720 . 
How is `Eid determined?
The differences among Muslims with regard to  `Eid Al-Fitr and  `Eid Al-Adha is based on this difference of scholarly opinion, and it is the same for both  `Eids. 
Shaykh Ibn Baz (may Allah have mercy on him) said, after mentioning the difference of opinion among the scholars about different moon sighting in different countries at the beginning and end of the month:                                            
“It seems to me that the differences in moon sightings do not matter , and that what must be done is to follow the sighting of the moon with regard to starting and ending the fast and offering the sacrifice when it is proven according to Shari`ah that the moon has been sighted in any land. 
Then he said: Whether or not we say that differences in sighting are valid, it seems that the ruling is the same for both Ramadan and  `Eid Al-Adha, and there is no difference between them according to what I know of Shari`ah.” (Majmu` Fatawa Ibn Baz (15/79) 
In the Fatwa of Shaykh Ibn `Uthaymin (may Allah have mercy on him) referred to above, it says that differences in moon sighting should be followed with regard to `Eid Al-Adha just as they are followed with regard to the beginning and end of Ramadan. 
Based on this, there is no problem if `Eid Al-Adha is on Friday in one country and on Saturday in another, and so on, based on the differences in moon sighting. 
The same may be said with regard to the fast of Ramadan, fasting the day of `Arafah and fasting `Ashura, because these are things that have to do with the sighting of the moon, and the ruling on whether the month has begun or not. 
And Allah knows best.