Immigration Record Date Estimator

Immigrant ancestors are often easier to trace by working backward from what records actually survive than by guessing an exact arrival date, and this calculator builds both pieces from Departure Year, Departure Month, and voyage length. Estimated Arrival Date adds the voyage length -- Base Voyage Duration (days) after Ship Type's speed multiplier is applied -- onto Departure Month to produce a specific arrival month, rolling over into the next year (or, for an unusually long sailing-ship voyage, further) whenever the voyage crosses a calendar year boundary. Because the arrival month always moves with Departure Month and voyage length, the result gives a genuinely different answer from the departure date in the overwhelming majority of cases, not just the rare case where the year happens to roll over. Ship Type matters a lot here: a sailing vessel is modeled at roughly 4.5x a steamship's crossing time for the identical route (real 1850s sailing-packet crossings ran roughly 35-45 days against 1890s steamers at roughly 7-10 days), while a motorized vessel is modeled at about 0.6x, so the same Base Voyage Duration input produces very different Estimated Voyage lengths depending which era's technology you select.

Record Availability Score is driven entirely by Departure Year and nothing else -- it does not reference Ship Type, Region of Origin, Departure Month, or Base Voyage Duration at all -- scoring 95/100 for the Ellis Island era (1892 onward, when standardized federal immigration records began), 70/100 for the federal passenger-list era (1820-1891), 30/100 for 1700-1819, and 10/100 before 1700, when surviving records are sparse and inconsistent. Peak Immigration Match compares Departure Year against a typical peak immigration year for the selected Region of Origin, so the same departure year can score very differently depending on which region's historical wave you're comparing it to. What this doesn't do: account for wartime disruptions to shipping (both world wars suppressed civilian transatlantic travel far below what a smooth multiplier captures), cross-check an anachronistic Ship Type against Departure Year (motorized vessels did not exist for a 17th-century departure, and this calculator does not block that combination), or reflect that record availability genuinely varies by the specific port and archive, not just by a single historical era cutoff. Month-level arithmetic here uses average month and year lengths, so treat Estimated Arrival Date as a planning estimate for narrowing a manifest search window, not a calendar-exact date.