In eHealth 6.1 and newer, the nhSnmpTool returns the sysUpTime in Epoch time format, this is a change from previous versions that returned the results in number of days, hours, minutes and seconds.
The change seen is caused by the underline Scotty library change. Scotty 2.x was used in eHealth 6.0 and Scotty 3.x is used in eHealth 6.1 or newer. nhSnmpTool uses same command to walk the target OID. Scotty2.x walk returns the days hours:minutes:seconds format, while Scotty 3.x returns epoch time format.
MIB dump uses epoch time in old and new Scotty lib. It appears a bit inconvenient for displaying the time in an interactive mode. But user can always convert it with a standard expression, for example Days = (sysUpTime)/100/3600/24 or use online Epoch time converter, as the one attached.