No, buying on Monday and selling on Tuesday is not a day trade. Buying on Monday at 3:59pm and selling at 9:31am on Tuesday is not a day trade.
Buying on security and selling that same security during the same trading day is a day trade. A trading day, for the purposes of day trading, is pre-market, regular hours, and aftermarket on the same day (Monday for example). It is not a 24 hour period.
Keep in mind that various brokers/firms have different rules regarding fund availability which has nothing to do with NASD/SEC day trading rules. For example, they might require a trade to settle before funds are availabile. This usually takes 3 days. Sometimes they only wait if the trade was an OTC or pinksheet. This depends on your broker and has nothing to do with daytrading.
As always, take that FWIW on an internet forum. Go to the source to be sure.
http://www.nasd.com/InvestorInformation/MarketsTrading/DayTradingInformation/NASDW_005906
What is a day trade?
Day trading refers to buying then selling or selling short then buying the same security on the same day. Just purchasing a security, without selling it later that same day, would not be considered a day trade.