Des que tinc aquest calendari, recordo millor cada data important.

Des que means since in a time sense: from the moment that.

So Des que tinc aquest calendari means Since I’ve had this calendar or Ever since I got/have had this calendar.

A useful distinction is:

• des que
  • verb = since
    • Des que visc aquí... = Since I’ve lived here...
• des de
  • noun/time expression = since/from
    • Des de dilluns... = Since Monday...

Catalan often uses the present tense after des que when English would often use the present perfect.

So:

• Des que tinc aquest calendari... literally: Since I have this calendar... natural English: Since I’ve had this calendar...

This is very normal in Catalan. The idea is that the situation began in the past and continues into the present.

They are related, but they are not used the same way.

• des que is followed by a verb clause
  • Des que tinc aquest calendari...
• des de is followed by a noun, date, or time expression
  • Des de l’any passat... = Since last year
  • Des de dilluns... = Since Monday

So you cannot use des de directly before tinc aquest calendari, because that is a clause, not a noun phrase.

Catalan has two common ways to say to remember:

• recordar
  • direct object
    • Recordo la data. = I remember the date.
• recordar-se de
  • noun/pronoun
    • Me’n recordo. = I remember it.
    • Em recordo de la data. = I remember the date.

In your sentence, recordo is the simple transitive verb recordar, and the thing remembered is cada data important.

So:

• recordo millor cada data important = I remember each important date better

This is completely natural.

Millor means better.

Here it works as an adverb modifying recordo:

• recordo millor = I remember better

Compare:

• bé = well
• millor = better

So the sentence says that, thanks to the calendar, the speaker remembers important dates better than before.

The adjective is important, and it has the same form for masculine and feminine singular in this case.

• un dia important
• una data important

So data is feminine, but the adjective still stays important.

Also, adjectives usually come after the noun in Catalan, so:

• data important = important date

Because cada already means each/every, and it normally goes directly before a singular noun:

• cada dia = each day / every day
• cada setmana = each week / every week
• cada data important = each important date

You would not normally say cada la data or cada una data.

That is just how cada works in Catalan. It is followed by a singular noun, even though the meaning is distributive and may translate as every or each.

Examples:

• cada alumne = each student
• cada any = every year
• cada data important = every important date

This is similar to English, where every date is also singular.

Yes, but the nuance changes a little.

• cada data important = each important date / every important date
  • emphasizes one by one, individually
• totes les dates importants = all the important dates
  • refers more to the whole set

So both could work, but cada gives a sense of remembering every single important date.

Aquest means this.

Because calendari is masculine singular, the form is:

• aquest calendari = this calendar

Compare:

• aquest llibre = this book
• aquesta data = this date

So:

• masculine singular: aquest
• feminine singular: aquesta

The comma separates the introductory subordinate clause from the main clause:

• Des que tinc aquest calendari, = time clause
• recordo millor cada data important. = main clause

This is very natural punctuation in Catalan, and it also helps readability.

To some extent, yes, but the given order is the most natural and neutral.

Standard order:

• Des que tinc aquest calendari, recordo millor cada data important.

You could sometimes move parts around for emphasis, but this version is clear and idiomatic.

Also note that important normally comes after the noun, so data important is much more natural than putting the adjective first.

A more word-for-word version would be:

Since I have this calendar, I remember better each important date.

That is not the most natural English translation, but it helps show the structure:

• Des que = Since
• tinc = I have
• aquest calendari = this calendar
• recordo millor = I remember better
• cada data important = each important date

So the natural English translation may differ a little, but the Catalan structure is straightforward once you see how the pieces fit together.