The preposition "desde" 
Is the equivalent of the English "from" and "since" in phrases relating to time -date or place - position.
It usually indicates some sort of motion in either time or space from a certain point.
"Desde" followed by a noun, by a time, by a date, by a place, to indicate when or where an action begins.
Desde Miami te envío esta postal….  I sent you this postcard from Miami.
Desde niño mostró su amor por la música. Since he was a child he showed his love for music.
Esta oferta está desde hace tres dias. This is on sale since three days ago.
Nos conocemos desde el año pasado. We know each other since last year.
It express the start of a period of time or the starting point.
Abierto desde las 9 hs. hasta las 17 hs. Is open from 9:00 AM to 5:00 PM
Las clases son los lunes desde las 10 hs. hasta las 14hs. The clases are Mondays from 10:00 AM to 2:00 PM
Las tarjetas comenzarán a estar listas desde el próximo lunes. The cards will start to be ready from next Monday.
Los uniformes los enviaremos desde el martes en adelante. The uniforms we will send them from next Tusday and so on
Desde 04/30 hasta 05/04 no estaré en mi oficina...      From 04/30 to 05/04 I will be not in my office...
Los materiales estarán disponibles desde el próximo lunes. The materials will be available from the next Monday
If you would like to know how long something has been occuring then you can begin your question with the phrase 
¿Desde cuándo...? Since when...?, or How long…?
¿Desde cuándo tiene usted éstos perros? How long have you had these dogs? 
To answer this type of question, you can begin your response with the word "desde".
desde anoche  since last night
desde anteayer   since the day before yesterday
desde ayer  since yesterday
desde el sábado   since Saturday
desde hace dos meses   since two months ago
desde el año pasado   since last year
desde el mes pasado   since last month
desde esta mañana   since this morning
desde esta tarde   since this afternoon
desde hoy   since today, from today
desde la semana pasada   since last week
Jack ha vivido en Londres desde 1994. Jack has lived in London since 1994.
Ha estado lloviendo desde ayer. It has been raining since yesterday.
La población ha aumentado mucho desde el último censo. The population has increased a lot since the last census.
Estoy a régimen desde esta mañana. I'm on a diet since this morning. I'm on a diet from this morning on.
Puedo ver el mar desde mi ventana I can see the sea from my window.
Quiero ver la película desde la última fila. I want to see the movie from the last row

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