So, you came to Montenegro for a holiday and you’ve fallen in love with the country and want to stick around and enjoy the beaches and the mountains for the rest of the summer.
Hey, it happens.
In 2018, I booked a week-long trip to a small town I’d never heard of called Kotor. That trip stretched to ten days, then I returned for another two weeks, then for the rest of the summer. A solid few days were wasted frantically combing the internet to figure out exactly when my 90 day stay would expire.
In some countries you can just pop over the border to a neighbouring country and return the same day with a fresh entry stamp to reset the count (and I have heard stories of people doing the same in Montenegro), but one of my golden rules for travel is don’t mess with immigration rules (or officials).
If, like me, you hold a passport from an English-speaking country like Australia, UK, US, Canada, or New Zealand, you can just show up without a visa and you will receive a 90 day stamp on arrival.
You can then use it all up in one go and stay continuously for 90 days. Or, you can travel in and out for a total of 90 days in 180 days, counted from the date of your first entry. After 180 days, the counter will reset and you’ll have a fresh 90 days.
For example, you flew in on March 1st and stayed 90 days in a row. You’ll have to leave on May 30th, then you can come back on August 29th.
Or, you flew in on March 1st and stayed for a week. You left and then came back in April at Easter for two weeks. You left again and then returned on June 15th. You now want to stay for as much of the summer as possible. At this point you have used up 21 days out of the 90 days from your first entry, so you have 69 days left, and you can stay until August 23rd.
Note that this is calculated differently from how much time you can spend in the Schengen zone in the rest of Europe. Their rather complicated system is a rolling count of the number of days you have spent in any 180 day period (if you’re still trying to figure it out, this Schengen calculator is helpful).
Montenegro’s system is much simpler as you only need to count the number of days since you first arrived (just remember to also count the day you arrived and the day you leave).
So, short answer: you can stay 90 days in 180 days, counted from the day you first arrived in the country. Enjoy your stay!