Is it too late for a Tu b’Av post? The first Mishna in Rosh haShana tells us that 1 Tishrei is the new year for netiyos, plantings. Assuming chodesh echad bashanah chashuv shanah, a plant must be around for one month in the year for it to count as a year, the plant must exist from Elul. On top of that one month, it takes (according to some Tanaim) 2 weeks for a plant to root. The Bartenura therefore writes that to count as a year of growth before Tishrei, planting must occur no later than Tu B’Av.
Achronim ask: the Bartenura’s cutoff point seems to be off by a day, as miktzas hayom k’kulo would allow one to plant on 16 Av and still make it!
The Noda b”Yehudah (II: O.C. 84) answers: miktzas hayom k’kulo only applies when counting days, i.e. it is a din in the shiur of what constitutes a "yom". When it comes to planting, the shiur is not 14 days, but rather is two weeks, which is not the same thing - you can’t use miktzas hayom to complete the shiur of required weeks.