Webmail problem on plesk 6.5

[itisl]

Hello,

i am using webmail to check my mails. i see that in my inbox some message are showed by time and some message are showed by date. the date i see is the wrong date. i tried to change by going to option and in display i put show me by time after receiving few mails again its show my date and which is the wrong date

Please help me what would be the probelm