In Terraria there are many events that are occur randomly such as the solar eclipse. Even after you have fulfilled the requirements for a solar eclipse is still only happens randomly (on the console version, the desktop ways create one via solar fragments).

Here are the steps to speed up invoking a solar eclipse (this will also work for a blood moon if you do it before night time). Please note, day time in Terraria starts at 4:30am.

• Turn the auto save setting off.
• Wait until 4:25am game time and save your game.
• Wait until after 4:30am, if no solar eclipse happens exit the game and DO NOT SAVE.
• Re-enter the game, it will be just before 4:30 again.
• Repeat this until a solar eclipse happens.

Although this might still be cumbersome it is much faster than waiting throughout a full day/night cycle. Note, you must still fulfill the other requirements before it will happen (e.g. you must beat at least one mechanical boss).