If the IRS is randomly reviewing my return and says it will be 45 days after March 16,2020. When is that exactly? I've gotten nothing in writing

Settle in for a long wait ... not sure if you heard the IRS was practically shut down for the last month and all reviews were put on hold.  All you can do is wait for more communications ... watch the IRS tool for any movement :  https://www.irs.gov/refunds