The Grand Ayatollah Khamenei answered a question about the start of the Khoms year.
Question: Is there any problem if the start of the Khoms year coincides with a special day of the lunar year for example Eid-ul-Ghadeer?
The Grand Ayatollah Khamenei: The person, who is responsible to pay Khoms, is free to calculate Khoms according to solar year or lunar year.
Source: khamenei.ir