As others have said, nothing worng with that for a mechanical. COSC specs for a mechanical are -4 to +6 seconds a day.

Do you lay it on it's side when you take it off? If so try laying it on it's back and you may find it more accurate.

Assuming we're talking about an automatic, that's pretty good.

new update, i think my getting slow 5 sec every day or two.

And i think it's getting slow when the date change. Am i wrong? anyone else have same problem?

Don't mean to nitpick, but anything that robs power from the mainspring will affect the rate, albeit ever so slight. The date change is driven off the motion works at the hour wheel. There are usually intermediate wheels, springs, etc. that are in play during the process. This means there is less energy being imparted to the going train. If the movement has poor isochronism (the ability of the movement to keep that same rate as the mainspring unwinds), the impact will be greater if the date change occurs when the mainspring is close to being unwound. That is why it is so important to minimize friction in all parts of the movement. Polished pivots, squeaky clean jewels, correct endshake, proper oiling, the list goes on, all contribute to isochronism.

So, you might try winding it at different times of the day and monitoring the rate difference. For example, if you fully wind it at night for a few days and log the rate difference; and then fully wind it in the morning for the same number of days and again log the rate difference, you should not see any significant difference between the two averages. Be sure to check the rate at the same time of day for both tests.