This weekend, overnight between Friday and Saturday, Mongolia changed to summer time. Contrary to Europe or the United States, it's a real novelty here, or let's rather say that it's the putting back of what existed nine years ago. Last time Mongolia changed to summer time was in 2006... and 2015!
Travellers probably received an email informing about the change of schedule of their flights. You'll arrive in Mongolia and leave the country one hour later. It can seem really unimportant, but it's a real good news for those who'll visit the country during summer. Indeed, in summer, sun rises early, at around 5AM, and goes down at around 21. Now, you'll have sun only from 6 AM, but you'll enjoy it until 22. At night, temperatures quickly drop, so this change will pleasantly prolong your evenings.
Personnally, I regretted that Mongolia had cancelled the switch to summer time, and I was glad to hear that the former system would come back. Now there will all year long be a time difference of 8 hours between Ulan Bator and London, of 13 hours between Ulan Bator and New York, of 16 hours between Ulan Bator and San Francisco.