The Statistics History display lets me see how the level of spam is progressing over time. Unfortunately the graph is based on the dates that the recipient opens (receives) the email messages.
This means that if I go on holiday for 20 days, when I return home and download the 20 days worth of emails, the history graph shows no emails received for the 20 days when I was away and then a big blip on day 21 when I download the backlog of messages.
This part of the graph is no good for comparing the trend of spam emails. Also the vertical axis of the graph is automatically adjusted to cope with this big blip so that most of the graph is now running just above the bottom axis.
It would be much better if the graph was based on the dates the the emails were POSTED by the senders. This would enable the graph to show what happened over the period when I was on holiday - all 20 days when I was away would show their share of emails - and I believe make the graph more useful.

MailWasher History Graph.jpg
Description:	Example showing what happened when I went on holiday for only 7 days
Filesize:	36.31 KB
Viewed:	28 Time(s)

The dates the emails were POSTED by the senders is often forged. Better to use the time your ISP accepted the message at their server.

Would it be possible to give the option to either display the History using the date/time the emails are downloaded OR the date/time that the emails were posted?
I still feel that in my example of the History display it would be more useful and informative to show an even spread across the dates.
There is also the issue of the vertical scale on the History Graph being stretched to accommodate the big blip if the received/download date is used.

I'm sure they could add that as an option but I'm confused as to why you want to use the dates that are likely to be forged by spammers rather than the valid date added by your ISP when the message is accepted there.

How do you want MW to display a spam that has 1-1-1980 as the date sent or 12-31-2036 as the date sent?

I agree with stan_qaz - keep the old default date for simplicity, and add an option to find the date received by the ISP using a custom-built regexp (since presumably each ISP is liable to use their own dating system)