Braavo Analytics allows you to view trial conversion rates with much more granularity than iTunes Connect's single, 30-day rolling average. You'll find it under the Subscriptions tab > Trials > Conversion.
Source: iTunes Connect > Subscription event report
Unlike other trial metrics, trial conversions are grouped by trial initiation date, rather than conversion event date. Trial conversions are available in three different views:
Conversions: the sum of Start Introductory Price + Paid Subscription from Introductory Price + Crossgrade from Introductory Price + Upgrade from Introductory Price + Downgrade from Introductory Price events.
Value: Conversions * Average Subscription Price (ASP)
Percentage: Conversions / New Trials * 100