Earnings Silly Season
Many companies publish their full year earnings in early April making this time of year the earnings season which is often called the Earnings Silly Season. It gets its name because share prices often appear to have a "silly" or nonsensical response to the earnings figures published.
For example, a company's earnings may exceed expectations and yet the share price drops after the announcement. This obviously is a non-logical and "silly" response to the earnings report.
Many companies publish their earnings in April because their financial year ends on 31 December and it takes 3 months for the accountants to compile the figures.