As Japan comes out of お盆 (o-Bon, a time to honor ancestors), conversations around the coffee machine at work are likely to center on people's 夏休み (natsu yasumi, summer vacations): "お盆休みはどうでしたか？" ("O-Bon yasumi wa dō deshita ka?," "How was your o-Bon holiday?") is one thing you're likely to hear, "実家に戻られました？" ("Jikka ni modoraremashita?," "Did you go back to your hometown?") is another.
Prior to the holiday, however, one word that likely popped up a lot in conversation was 予定 (yotei, schedule). It's not uncommon to hear 予定 in an office setting at any time of year, but the Japanese also use it to refer to plans they have outside of work: 今週末、鎌倉に行く予定があります/を立てました。 (Konshūmatsu, Kamakura ni iku yotei ga arimasu/o tatemashita, I have plans/made plans to go to Kamakura this weekend).
The verb 立てる (tateru) is used when you want to make a plan, and it's used when you want to break one: すみません、予定が立たないので欠席します (Sumimasen, yotei ga tatanai node kesseki shimasu, I'm sorry, I must decline as I'm unable to fix my schedule). Having said that, 予定が立たない is used more often before plans are made because you can't fix your schedule. When you're talking about things falling apart after the fact, reach for the verb 潰れる (tsubureru): 忙しくて夏休みの予定が潰れた (Isogashikute natsu yasumi no yotei ga tsubureta, I was busy and my summer vacation plans fell apart).