Hey there! I am responding on this as part former destination wedding bride (in Akumal) but also as a wedding photographer.
It looks like during that time of year, the sun will set in Tulum between about 6:10 p.m. and 6:20 p.m. You can always check on the exact time using this site (this is what I use for my clients when trying to determine the best time to take photos near sunrise and sunset): https://www.timeandd...th=12&year=2018
Since the sun sets on the opposite side of the beach in that area, you will quickly lose light if you're too close to sunset, which sounds like it may be the case if you schedule your ceremony at 5:30 p.m. Also it really depends on the following:
- how long will your ceremony be?
- do you plan on doing group/family photos afterwards?
- do you plan on doing romantic portraits with our spouse afterwards?
If you do plan on doing portraits after the ceremony, I would suggest leaving your time at 4 p.m. Wedding Days are unpredictable and timelines can often run late for whatever reason. Keeping your ceremony at 4 p.m. gives you a lot of wiggle room before you completely lose sunlight -- at least 2 solid hours to work with. If you change it to 5:30 p.m., you realistically only have about 40 to 50 minutes of sunlight.
This is all dependent on what style of photos you prefer as well -- if you're looking for light and airy images, then definitely keep your time at 4 p.m. If you want more dramatic images with the sunset and artificial lighting, then you can definitely chance it at 5:30 p.m. (Also keep in mind, it depends on the shooting style of your photographer).
If you've hired a photographer, I would definitely ask for his/her professional opinion, their style may dependent on the lighting conditions!!!
Hope that helps