I have content query web part for displaying the future events. But the web part is displaying the past events as well. For example, I had two events in March and 3 in April. It shows all five event. I want it to show only April events.
Look in the web part properties for the filter settings. You can choose a date column and date filter criteria to apply to the content query web part. For example, you can configure a filter on an Announcements list for items created "greater than" today.
See more on standard filters a similar thread on MSDN Forums.
If the field you want is not displayed in the filters list, download the .dwp file and modify it manually to add the field. MSDN has a walkthrough of the specific steps required.
Created and Modified are in the filter list but not some other time and date fields. For example, the start date and end date fields of a calendar list are supported by the content query web part when you manually edit the .dwp and add the fields in as described on MSDN.