There are visas which are read in different ways depending on the countries:
1st – These are Straightforward Visas. For example UK, USA visas, where you have a visa validity start (Valid from) and end date (Valid Until) which is self-explanatory. The visa is valid for a specific period of time and you have to travel and return within that period.
2nd – These are similar to Schengen visas, where you have a start and end date of validity (Valid From and To) and also there is duration of stay in Days along with number of entries. This means you can travel within that specific period of time but the duration cannot exceed the total number of days granted. For Example, Duration (start and end date) might be granted for 6 months and days might be given only 30 days, which means within that 6 month period, you can stay in the country only for 30 days only.
Besides you also have to check the number of entries granted. It can be single, double or MULT (multiple), so if there is single entry issued then you can travel only once and your stay cannot exceed 30 days. If double entry is granted, you can make 2 trips and the duration combining both travels cannot exceed 30 days. For multiple you can make multiple trips but cumulative duration of stay cannot exceed 30 days.
3rd – These are entry visas, where you have a start and end date (issue and expiry date) and there is also remarks where specific duration is granted, most of the time it’s issued for 30 days or more, depending on the country. In this case, you can travel any day as long as, it’s within the validity period, however you can return even after the expiry date of the visa and you cannot exceed 30 days or the number of days granted. In short you need to land in the destination within the validity period but return can be before or after the visa expiry date, but ensure to comply with the duration granted for the trip.
In brief when you travel, please don’t stay in the country till the last day of the expiry date, always keep few days buffer to keep any natural calamities/delay. If you end up on the last expiry date and you are stuck at the airport, do remember being a foreign national you have to procure an emergency visa and then travel, this is going to complicate the situation further.
If you need any further advice, am just an e-mail away, do reach out to me at firstname.lastname@example.org