Its pretty clear it was just after his baptism that they went full time following Jesus on his three year evangelistic ministry. Some think his ministry was only six months long though, other s claim only a year and a half, so maybe that was what he was thinking but I think for those numbers you really have to mess with the scriptures structure too much.
John Young's post in Easter was marked as the answer
Ten Years after the resurrection of Christ we find that the church in Jerusalem is prospering and the Jews are becoming more and more jealous of the popularity of Christ. This was particularly felt during the Passover week (days of unleavened bread), as the Christians focused less on the Exodus aspects of Passover and more on the Christian aspects culminating with Easter (sunrise) morning Resurrection on the first day of the week after.
On this tenth anniversary of the crucifixion Herod wanted to please the Jews by harassing the church by taking Apostle James and executing him. Seeing this pleased the Jews, Herod took Peter to hold him in prison until after the resurrection anniversary the church was going to observe. However, God confounded Herod's efforts similar to the attempts of the Jews at the tomb of Christ by freeing Peter form the prison and guards.
Being embarrassed by his failure, Herod leaves town and dies a year latter (probably on Passover day) attempting to take the Glory of God for himself. In this sermon we note that Easter and Herod are not Pagan.
Easter refers to the Christian events of the Passover Week and the Resurrection at sunrise in particular. We also note how Herod sought to please the Jews and how he is a type of the Anti-Christ.
Another thing about Spurgeon is that he never let Theological intellectualism to get in the way of the practical commands of scripture. So while he was a Calvinist he was also very concerned with carrying out the great commission through evangelism. Also if one looks beyond his Calvinism and into most of his messages they will see a person more in line with today's Fundamentalist Baptist than with today's Reformed Calvinist.