Answer:
This means that the tenses do not agree, more like Concord.
Step-by-step explanation:
Concord in grammar means subject-verb agreement. That is, if a verb is in the singular form, then the subject must be in the singular; and if it is in the plural, then the subject must be in the plural.
When a writer makes a mistake of disunity in tenses, it means that the sentence does not follow the subject-verb rule.
For example,
The group of dancers is here is wrong because the dancers are in plural, but the singular verb is is used.
Correcting the sentence,
The group of dancers are here.