Ordinary words and the like, the longer the age, the higher the value, and the time of the work will be marked on the calligraphy works. I have seen an old one at my brother-in-law's house before the Republic of China. The exact time is unknown. You can look for a professional to study it.
The second standard: the paper of calligraphy works, that is, color difference.
As we all know, in this era, many things can be forged, such as the age of your work itself, to a certain extent, many non-professionals can't find it.
However, many calligraphy works themselves, that is, the age of paper, cannot be forged, because many papers will be very broken after time erosion.
When you look at it, you will find that the color of paper is actually a good example, but everything old is yellower.
It is easy to know whether this is true or not except in professional inspection. As long as it is forged, reference to modern technology will be exposed.
Secondly, the paper material of calligraphy itself is an important foundation. In previous times, their paper was different from our modern paper. Now it's exquisite, and most of the previous ones were rough. The longer it is preserved, the higher the possible degree of erosion.
The third criterion: the author of calligraphy works.
The advantage of the work is the author's popularity. Everyone will write their own works, but because of different authors, their values are different. Calligraphy written by a famous person is of high value. The fewer people want to collect.
There is also a place to display works. If it is in a very strict exhibition hall, it is definitely more precious, but there are almost no fakes, and some are still collected by the state, and their value is priceless. To sum up, it is the value of the work itself, and some may change due to geographical reasons.