This example uses a standard Date property but you'd simply use a Created Time property instead.
Stage
if(now() < prop("Agreements by"), "📝 Agreements", if(now() > prop("Agreements by") and now() < prop("Implement by"), "🛠 Implement", if(now() > prop("Implement by") and now() < prop("Invoice by"), "💰 Invoice", if(now() > prop("Invoice by") and now() < prop("Report by"), "📊 Report", ""))))
Stage (Combined)
if(now() < dateAdd(prop("Created"), 14, "days"), "📝 Agreements", if(now() > dateAdd(prop("Created"), 14, "days") and now() < dateAdd(prop("Created"), 20, "days"), "🛠 Implement", if(now() > dateAdd(prop("Created"), 20, "days") and now() < dateAdd(prop("Created"), 30, "days"), "💰 Invoice", if(now() > dateAdd(prop("Created"), 30, "days") and now() < dateAdd(prop("Created"), 45, "days"), "📊 Report", ""))))
