Question: "What is Spy Wednesday / Holy Wednesday?"
Answer: In Christianity, Holy Wednesday or Spy Wednesday is the last Wednesday prior to Easter Sunday; it is the fourth day of Holy Week after Palm Sunday, Holy Monday, and Holy Tuesday. Depending on the denomination, this particular day may or may not be celebrated at all. Those that do observe Holy Wednesday, such as Eastern Orthodox churches, typically mark it with readings of Scripture and the singing of relevant hymns.
According to the traditional interpretation of the Bible, Holy Wednesday is the day on which Jesus was anointed with spikenard during a meal (Matthew 26:6–13). The day is sometimes called “Spy Wednesday” since it is traditionally thought of as the day Judas conspired with local authorities to betray Jesus (Matthew 26:14–16). The following day is sometimes referred to as Maundy Thursday, the fifth day of Holy Week.
The Bible does not mention Holy Wednesday or Spy Wednesday. And it should be noted that events within the Gospels were not necessarily arranged chronologically, following the fashion of similar works written during the same time period. Also, the chronology of each Gospel was affected by cultural rules, as Roman and Jewish days started at different times. For these reasons, it’s unwise to be dogmatic about precisely which events occurred on which days leading up to Jesus’ arrest and crucifixion.