What if the individual had an HSA before opening a UMB HSA? What is the HSA establishment date then?

If a new UMB HSA accountholder has another HSA, their establishment date is considered to be the date of the other HSA. The UMB HSA is deemed to be established when the first HSA was established if the prior HSA had a balance greater than zero at any time during the 18-month period ending on the date the later UMB HSA was established.