In China, the fourteenth century should be the Ming dynasty

Situation: I'm guessing what era/dynasty/time it was in China in the 14th century:

-In China, the fourteenth century should be the Ming dynasty.

But to refer to a past thing, we need the past tense.

You're not referring to anything that is past, WB. You are describing an historical fact - sort of similar to; The Ming Dynasty should fit right here [pointing to the 14th century] in this historical time line.

According to the 'SHOULD DO for now; SHOULD HAVE DONE for past' rule, must I change SHOULD BE to SHOULD HAVE BEEN in my sentence? I become more unsure because a change like this would give me the impression that the Ming dynasty didn't exist, though SHOULD HAVE DONE doesn't necessarily tell us something that was possible/expected to happen but didn't.

The Ming Dynasty ... WAS the ruling dynasty of China for 276 years (1368–1644) following the collapse of the Mongol-led Yuan Dynasty

From his first book in 1898 until his second stint as Prime Minister, Churchill's income was almost entirely made from writing books and opinion pieces for newspapers and magazines

TO WILLIAM BUTLER YEATS




TELL us of beauty! Touch thy silver lyre
And bid thy Muse unfold her shining wings!
Tell us of joy—of those unaging things
Which wither not, nor are consumed by fire,
Things unto which the souls of all aspire!
Sing us the mystic song thine Erin sings,
Her poignant dreams, her weird imaginings,
With magic of thy "Land of Heart's Desire!"


Let others hate!—from lips not thine be hurled
Reproaches; since all hate at last must prove
Abortive, though it triumph for a while.
The gospels that indeed have won the world
Laid their foundations in the strength of love.
Sing thou, a lover, of thy wave-washed Isle

You are describing an historical fact - sort of similar to; The Ming Dynasty should fit right here [pointing to the 14th century] in this historical time line.

In nine cases out of ten, WAS cannot be changed to IS, though 1895 being that year is indisputable fact.

For 'Mr Churchill should be/should have been a modern writer.', my meaning is like this:

Look here! Here's a sentence by Winston Churchill, but he says 'blackmails'! In modern English, 'blackmail' is not used in the plural form, is it? But Winston Churchill should be/should have been a modern writer, how come he uses non-modern English in his works?

Which tense should I use?