Oman has made a departure from the usual practice of only announcing the start of Ramadhan, and other religious events, by actually sighting the Cresent Moon the evening before the date.
Oman’s Ministry of Awqaf and Religious Affairs has announced the date of Ramadhan 10 days in advance. Ramadhan Announcement Oman 2018
They have announced that the month will start commencing 17th May 2018.
This is the 1st time Oman has used an astronomical calculation for this, a way of helping make such a decision that is under consideration elsewhere in the Islamic world. The subsequent Eid is therefore also likely to have the same methods applied as, from a mathematical calculation viewpoint, the movement of heavenly bodies is now known with remarkable precision. Whether it will apply to Eid al Adha which falls during the month of Haj and therefore may need some consideration for the announcement by Saudi Arabia, remain to be seen