Charles Spurgeon Commentary Acts 1:7-8

"And he said unto them, It is not for you to know times or seasons, which the Father hath set within His own authority. But ye shall receive power, when the Holy Spirit is come upon you: and ye shall be my witnesses both in Jerusalem, and in all Judaea and Samaria, and unto the uttermost part of the earth." — Acts 1:7-8 (ASV)

As indeed they were, for they went everywhere testifying to what they had seen and heard, and very many were the conversions that followed. We want the same power to rest upon us now that rested upon them when the Holy Spirit came upon them.