Logs are ordered by day, but within the same day by the time the log is written. (Even if you indicate the time you found the cache in the text, this is not taken into consideration, nor is there any other possibility to indicate the time.) In addition, it’s the person writing the log who chooses the date, and surprisingly many people do not even bother to choose the correct date in their logs. (Which, BTW, can be very annoying e.g. when it comes to "found it" logs in a row of DNFs. Or simply strange when you see attended logs on an event which took place days before.) Having said that it is up to you to decide how you define a "day" for yourself, i.e. wether you use always the time/date of your home base or whether you use local day/time. (I personally always use the local time.) So, if you log the the five countries with the same date, they will be used for qualifying for the challenge, irrespective of when you write the log (or when you find them, for that matter; the system will never know whether anybody is cheating with regards to the date.)