The correct answer is A. remember.
The other options are incorrect because they are not in the simple present tense. The simple present tense is used to talk about things that happen regularly or are always true. In this case, the speaker is saying that this date is worth remembering, which means that it is a date that should be remembered on a regular basis.
Option B, to remember, is in the infinitive form. The infinitive form is used to talk about things that are possible or necessary. In this case, the speaker is not saying that it is possible or necessary to remember this date. They are saying that it is worth remembering.
Option C, remembered, is the past participle of the verb remember. The past participle is used to form the perfect tenses and the passive voice. In this case, the speaker is not talking about the past or the passive voice. They are talking about the present.
Option D, remembering, is the present participle of the verb remember. The present participle is used to form the progressive tenses and the gerund. In this case, the speaker is not talking about the progressive tenses or the gerund. They are talking about the simple present tense.