The article features a temporal approach to analyzing the impact of Western colonialism on contemporary levels of democracy. We present a new data set with dates of colonization, independence, and a colonizing event for all former colonies and dependencies that are regarded as countries today (143 observations). Our data, as well as the existing literature, suggest that the very heterogeneous era of colonization should be divided into an early ‘mercantilist’ wave and a much later ‘imperialist’ wave with quite different characteristics. We show that there is a strong positive effect of colonial duration on democracy, an effect which turns out to be driven primarily by former British colonies and by countries colonized during the imperialist era.