Hi! Could you please tell me if I can specify the end date of the experiment before its launch?

Try 'edit phases' section and set future date for end time. I have not tested if that actually works. Another idea could be using API to stop given experiment, running it e.g. in crontab

Thanks, I've seen this method, but I also haven't tested it. I thought there might be an alternative way to set the dates at once, for example 2 weeks.