I assume that what you are seeing is the internal representation of an Excel date/time. The integer portion of the value is the number of days since 01/01/1900 and the decimal portion is the proportion of the day( .25 is 6AM, .5 is 12 noon etc. ). However, when I take 44439,1151041667 and feed it into Excel, I get 08/31/2021 02:45:45. Is it possible you are showing the values from 2 different cells?
What version of JMP are you using, and what operating system?
Jim