Ever since: 自从……(以来/以后)
介词 / prepositions
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
自从 + time / event + (以来 / 以后)，…
自从 (zìcóng) = "ever since". It marks the starting point in the past of a situation that lasts until now (or has changed since).
You often add 以后 or 以来 at the end of the phrase: 自从有了手机以后…, 自从去年以来…
Difference from 从: 从 can mark a start in the past or future (从明天开始), while 自从 is only for the past.
Examples
自从有了智能手机，我很少看报纸了。
Zìcóng yǒu le zhìnéng shǒujī, wǒ hěn shǎo kàn bàozhǐ le.Ever since I got a smartphone, I hardly read newspapers.
自从他搬走以后，我们就没见过面。
Zìcóng tā bānzǒu yǐhòu, wǒmen jiù méi jiàn guo miàn.We haven't seen each other since he moved away.
自从去年以来，网上买东西的人越来越多。
Zìcóng qùnián yǐlái, wǎng shang mǎi dōngxi de rén yuè lái yuè duō.Since last year, more and more people have been shopping online.
Common mistakes
✗ 自从明天开始 → 自从 is for the past only. ✓ 从明天开始。
✗ 我学中文自从去年。 → the phrase goes first. ✓ 自从去年，我开始学中文。