Remember The Milk is one of the original web-based task managers — launched in 2004 and still actively developed, with a loyal user base who appreciate its maturity, reliability, and deep integration with Gmail, Google Calendar, Twitter, Evernote, and Alexa. Its Smart Add feature parses natural language task input, and its Smart Lists let users create filtered views based on any combination of tags, due dates, priorities, and locations. RTM's longevity — over 20 years — is a testament to getting the fundamentals exactly right.

Reference:

Remember The Milk on Wikipedia

https://en.wikipedia.org/wiki/Remember_the_Milk