Definitions of earlier:

• adjective:   (comparative and superlative of `early') more early than; most early

  Example: "A fashion popular in earlier times"

• adverb:   earlier in time; previously

  Example: "He called me the day before but your call had come even earlier"

• adverb:   before now
• adverb:   comparatives of `soon' or `early'

  Example: "Came earlier than I expected"