Welcome to the forum shivetya!
If you know the exact date, hover over the ARCHIVES link in the navigation bar and CALENDAR option should drop down. Once you click on that, it should be fairly straight forward. Also the format
http://archives.sluggy.com/daily.php?date=YYYY-MM-DD will work as well
Unless you mean to be able to ONLY see the strip and not be taken to its location in the chapter. Not sure what they are doing with that. I hope they do. At least you don't download the entire chapter now.
Anyway, you may be here to post in the forum or you were confused and thought you needed to be a Full Member to participate in non-forum things. You don't actually. Whichever it was, means you can post in the forum whenever the urge hits you, if you want. Now I will tell you about the strange tradition aimed at newcomers.
At one time there were Pesterers who pestered you for poetry, but that tends to be very rare nowadays. Even though you may not be pestered, if you do go and post an original poem--usually haiku but any (clean) type is accepted--written by you, you will most likely receive a gift in return. The "gift" will most likely be useless or maim you...a little. Whichever it may be, it should be interesting and surprising. Lastly, this strange tradition applies to the pestering not the poetry. You are not required to do anything more to be a member here...unless you want a gift.
Now go forth and do (almost) whatever you want, just don't speculate in Reactions.