Delivery dates at checkout that respect warehouse capacity

Shopify Community threads struggle to put real date pickers and ETAs on checkout. ShipManta Delivery Calendar enforces lead time, cutoffs, blackouts, and daily caps.

The problem

The buyer picks a Friday the dock cannot hit. Support moves dates by hand. Capacity and vendor rules never made it into checkout.

What stores report

Merchants and partners ask how to add a checkout date picker, how to recalculate shipping when the date changes, and how to show estimated delivery for custom rates — not only Shopify’s built-in methods. Static “ships in 7–10 days” copy does not protect a dock with real daily limits.

How ShipManta solves it

Delivery Calendar is a checkout app driven by the same engine the warehouse trusts. Lead time and cutoff set the first offerable day. Allowed weekdays and blackouts remove closed days. Daily shipment and product caps close a day when either limit is hit. Override rules can give vendor-specific windows (for example only the next three open Tue–Fri days) while still skipping full days.

After the order lands, diagnose tools show which calendar wrote the date, whether capacity applied, and whether the selected day was actually offered — so support argues from the engine, not from memory.

East-coast style caps: hit shipments or products and the day blocks
Vendor windows that still honor capacity
Metafield / attribute output onto the Shopify order
Test carts before you activate a rule

Where stores talk about this