Translation:I started learning Esperanto one year ago.
Why is Esperanto not la esperanta like other languages like la angla kaj la japana?
From the "Tips and notes" in "Languages 1":
When you refer to a language, you must have la in front of it, because it is short for la ... lingvo. For example, English is la angla, short for la angla lingvo.
Exception: most planned and dead languages end in -o and therefore do not use "la" in front of them. Thus, you would say, Mi parolas Esperanton and not Mi parolas la Esperanton. And you would say: Mi ne parolas Latinon (I don't speak Latin)."
You could and everyone would understand you, but I do not think it is really common.
Interestingly, originally Zamenhof (the creator of Esperanto) called the language "Internacia Lingvo", which follows the naming conventions of other languages.
But instead the language became better known by the pseudonym Zamenhof used to publish his first Esperanto book namely "Dr. Esperanto" or "Doctor One-Who-Hopes". So an Esperantist is someone who speaks the language of hope. It is very poetic.
I guess that makes sense. It would make a distinction between the country and the language but since a constructed language like Esperanto doesn't have a country, it would not need that distinction. Same with Latin.
Interestingly, you can call the language "la internancia", according to Zammenhof.