Which one is correct?
A partir de ahora, voy a hablar en español.
or
Desde ahora, voy a hablar en español.
In meaning I think both are close to "from." Are there any specific instances where one cannot replace the other.
Which one is correct?
A partir de ahora, voy a hablar en español.
or
Desde ahora, voy a hablar en español.
In meaning I think both are close to "from." Are there any specific instances where one cannot replace the other.
RAE:
partir:
intr. Tomar un hecho, una fecha o cualquier otro antecedente como base para un razonamiento o cómputo.
desde:
prep. Denota el punto, en tiempo o lugar, de que procede, se origina o ha de empezar a contarse una cosa, un hecho o una distancia. Desde la Creación. Desde Madrid. Desde que nací. Desde mi casa. U. t. en locs. advs. Desde entonces. Desde ahora. Desde aquí. Desde allí.
A partir de is used when an action is going to take place starting from that point on. You can indicate the end by using hasta.
Example:
A partir del lunes voy a hacer ejercicio.
A partir de mañana voy a empezar a estudiar hasta que presente el examen.
Desde means the same thing as a partir but the difference is that desde is used for actions that have already taken place and are still valid in the present or a specified point in time (you use hasta to indicate the end).
Desde el año 2004 en Europa se transmite televisión en alta definición. (and still being transmitted)
Los niños comenzaron a jugar desde que la maestra salió del salón hasta que la directora llegó y los regañó.
So which one is correct? It's difficult because of the ahora but for me as a native speaker it sounds more natural "Desde ahora...".
To simplify that.
A partir de ahora = starting now, from now forward.
A partir can be used to indicate a future starting point.
A partir de noviembre de 2012 = starting in November 2012, from November forward.
Desde is more like "since" (in the temporal sense only).
Desde will refer to a past starting point, and not a future one.
Desde noviembre = since November.
You would not say, for instance:
Desde mañana (since tomorrow).
Desde la semana que viene (since next week).
You would/could say:
A partir de la mañana (starting tomorrow).
A partir de la próxima semana (starting in the next week).
Desde works nearly everywhere, but a partir de only really works with sustantives.
"A partir de" is used frequently for resolutions, either personal resolutions like your example or "lawful" stuff ("a partir del lunes, las horas extras estarán prohibidas" [from Monday on, working overtime will be illegal]). It's also more natural if the point of time is just now or in the future, desde seems more natural for the past (i.e. hablo español desde el mes pasado; hablaré español a partir del mes que viene).
Please keep in mind that not every nd word in Spanish has a 'finite' translation form and that it can have different meanings in regards to colloquial differences. In Mex/Spanish, the direct translation of the phrase a partir de = 'apart from' = a partir <----these 2 words together are the equivalent of the single English word 'apart' and are usually used in reference to distinguishing a single characteristic which sets it apart from the rest.
The word de <----means from and in this case, the two words together would mean 'apart from'.
Although the word de usually means 'from', in this case, it can also be used as a point of reference and that can be in the form of juxtaposition as well as Geo-location and in abstract form as opposed as to the finite.
The Mexican word de can mean either from or of, depending on the content or object of the sentence and can be used both in the abstract form as well as the finite.
The direct translation of the Mexican word is both 'of' as well as 'from' and can also vary depending on the content and object of the sentence.
Desde ayer,Desde ahora,Desde mañana,Desde que te has ido, desde el día que se fue...