Downloading Mayday 4.3.1 for Mac from the developer's website was possible when we last checked. We cannot confirm if there is a free download of this app available. The program lies within Productivity Tools, more precisely Timekeeping. We recommend checking the downloaded files with any free antivirus. The actual developer of this free Mac application is Mayday Labs Inc.
From the developer:
Mayday is a smart calendar assistant tool that gives you control of your schedule and helps you spend time in more meaningful ways. Mayday develops a comprehensive understanding of demands on your schedule and helps you prioritize what matters most to you.
You may want to check out more software for Mac, such as Tea Timer, Missing Sync for Sony PSP or TimeMachineGrowler, which might be similar to Mayday.