Symptom: SNMP oid of sysUpTime OID: 1.3.6.1.2.1.1.3 is refreshed after 497 days. 

The time (in hundredths of a second) since the network management portion of the system was last
re-initialized.

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Instructions

Summary:
Citrix NetScaler has no 64bit SNMP OID for sysuptime. This is a by design because Citrix NetScaler is running over FreeBSD OS and it has no control on the underlying OS.
 
The sysuptime SNMP counter will be reset after: TIMETICKS: 497 days, 2 hours, 27 minutes, 52 seconds
As of now we have no solution to resolve this limitation.
 
Suggestion:
Please use the 'stat ns' command and check Up since column for reference.