Retirement tax questions

I have searched several sites, including the IRS, and cannnot find a "time limit" on how long one has to convert/transfer the funds from the deceased IRA owner account into the new inherited IRA account?   Strange, although I suppose there is a limit by proxy in that the new owner, like you say, must start taking RMDs and the new owner can't do that until they have established the new account.  

OK, thanks for info on RMDs.  I noticed the IRS published new life expectancy tables effective 2023 for Inherited IRA owners so, again, like you say, they probably will , finally, issue a rule stating RMDs are mandatory. 

Thank you.