Short answer
Your surgeon and medical team decide when you have surgery, and urgent or recommended treatment should never wait for astrology. If they offer a choice of equally suitable dates, some people prefer to avoid their Chandrashtama days, when the Moon passes through the 8th sign from their Moon sign. That is a personal comfort, not a medical factor.
How ChiChakra reads this
Traditionally, planned procedures are timed by the Moon, and Chandrashtama is the period most people avoid. ChiChakra shows your Chandrashtama days and the day's Rahu Kalam; it does not assess medical risk, recovery or suitability.
If you have a choice
Ask your team which dates are medically equivalent. Only then look at timing.
Check those dates against your Chandrashtama days. If the hospital sets the time of the operation, accept it; you rarely control the hour, and that's fine.
Put your energy into what helps recovery: the preparation instructions, transport home and someone to help for the first few days.
Good to know
Your doctor decides. A preferred day is a comfort for you, not a factor in the outcome.