ممكن نغير المعاد؟

You use this phrase as a complete question. You do not need much else to be understood. If you want to be extra polite, add لو سمحت (if you please) at the end. It is very flexible. You can use it in person, over the phone, or in a text message. Most people will follow it up with a reason, like 'I am stuck in traffic' or 'I have a lot of work.' It is a 'we' verb (نغير), which makes it feel collaborative. You are suggesting a change together, not just forcing your schedule on them. It softens the blow of canceling.

Use this when you realize you cannot make it on time. It is perfect for the dentist, the hairdresser, or a business meeting. It is also great for social life. If your couch is too comfy and you want to see your friend tomorrow instead, this is your phrase. Use it when you are running late and realize you need an hour, not ten minutes. It is also useful when a better opportunity comes up and you need to shift your day. Use it whenever a plan needs a little wiggle room.

Do not use this five minutes after the appointment was supposed to start. That is considered rude in almost any culture. Avoid using it for very high-stakes events like a wedding or a final exam. In those cases, 'changing the appointment' is not really an option. Also, do not use it repeatedly with the same person. If you change the معاد three times in a row, they might stop making plans with you! In very strict formal settings, you might want a more formal word like تأجيل (postponing), but for 90% of life, this phrase is fine.

In many Arabic-speaking cultures, especially in Egypt and the Levant, time is viewed as fluid. There is a famous trio of words: IBM. It stands for Insha'Allah (God willing), Bukra (tomorrow), and Ma'lesh (never mind/it's okay). This phrase fits right into that culture of flexibility. People generally understand that life happens. Traffic, family duties, or unexpected guests are common reasons to shift plans. While being on time is respected, being flexible is often seen as a sign of a good relationship. Changing a time is rarely seen as a personal insult; it is just life being life.

If you want to be more specific, you can say ممكن نأجل المعاد؟ which means 'Can we postpone the appointment?' If you want to move it earlier, you say ممكن نقدم المعاد؟. In more formal Modern Standard Arabic, you would say هل يمكننا تغيير الموعد؟. Note the slight change from المعاد (dialect) to الموعد (formal). If you are texting a close friend, you might just say نغير المعاد؟ without the ممكن. It is shorter and punchier for WhatsApp.