Symptom:
1. Difference in time between Parent switch and FEX switch. 
2. After you clear counter on FEX HIF (Host Interface) port, the Last clearing of show interface counter does not reset to 0 sec. Instead it resets to the time difference between Parent switch and FEX.
 
Example
 
switch# sh clock 
15:20:54.834 UTC Wed Jun 25 2014
 
switch# attach fex 110
Attaching to FEX 110 ...
To exit type 'exit', to abort type '$.' 
fex-110# sh clock 
15:12:28.273 UTC Wed Jun 25 2014
 
 
switch# clear counters interface e110/1/1
switch# sh int e110/1/1
Ethernet110/1/1 is down (SFP not inserted)
====Output Omitted ====
  Last clearing of "show interface" counters 00:08:42
 
The last clearing of the counter is 8 min 42 sec which is equal to time difference between Parent switch and FEX.

Conditions:
This problem is observed when the FEX Model is 2248PQ