DateTime of Last TVQ True Value

Is there a way to display the date of a Boolean tag of the last time it was True.  I have a customer asking to show when the last Downtime condition was reported.  This corresponds to the last time the Downtime Boolean tag was true.  Any ideas of how to display this or if it is even possible would be great.  I am also not afraid to script the solution in Axiom.  Thanks in advance!!