Business Day API Comparison: BizDay vs Alternatives

Why You Need a Business Day API

If your application calculates delivery dates, SLA deadlines, payment settlement windows, or invoice due dates, you need accurate business day logic. That means not just skipping weekends, but also accounting for public holidays that vary by country and change year to year.

Several APIs exist to solve this problem. This guide compares the most popular options to help you choose the right one for your project. We evaluate each on the criteria that matter most to developers: ease of integration, response time, country coverage, pricing, and the specific operations each API supports.

What to Look For

Before comparing specific services, here are the key factors to consider when evaluating a business day API:

• Business day operations: Does it just list holidays, or can it check dates, add business days, and count working days between dates?
• Country coverage: How many countries does it support, and how frequently is the holiday data updated?
• Response time: For user-facing features, latency matters. Sub-50ms responses are ideal.
• Pricing model: Does it offer a free tier? How does pricing scale as your usage grows?
• Developer experience: Is the API well-documented? Are the response formats consistent and predictable?
• Reliability: What is the uptime guarantee? Is the service built on a globally distributed infrastructure?

The Contenders

We compare four services that developers commonly consider for business day and holiday API needs.

BizDay API

BizDay is purpose-built for business day calculations. Rather than just providing holiday lists, it offers first-class endpoints for the operations developers actually need: checking if a date is a business day, finding the next business day, adding business days to a date, and counting business days between two dates.

curl "https://api.bizday.dev/v1/add?date=2026-03-09&days=5&country=US" \
  -H "Authorization: Bearer wday_your_key"

# Response:
# {
#   "success": true,
#   "data": {
#     "start_date": "2026-03-09",
#     "country": "US",
#     "workdays_added": 5,
#     "result_date": "2026-03-16"
#   }
# }

BizDay supports 30+ countries with holiday data synced weekly from government sources. It runs on Cloudflare’s global edge network, delivering sub-20ms response times from most locations. The free tier includes 10,000 requests per month.

Holiday-Only APIs

Services like Calendarific and Nager.Date focus on providing raw holiday data. They return lists of holidays for a given country and year, which you then use to build your own business day logic.

This approach gives you flexibility, but it means you write and maintain the date arithmetic yourself. You handle weekend definitions (which vary by country), observed holiday rules, and the caching layer for holiday data. For simple use cases, this may be fine. For production systems that need reliable business day calculations across countries, it creates ongoing maintenance work.

General-Purpose Date APIs

Some general-purpose APIs include holiday data as part of a broader offering. These services often bundle timezone conversion, date parsing, and holiday lookup into a single product. The trade-off is that business day operations are rarely the primary focus, which can mean fewer dedicated endpoints, less frequent holiday data updates, and slower response times due to the broader feature set.

Feature Comparison

When Each Approach Makes Sense

Choose BizDay When:

• You need business day operations, not just holiday lists
• Your app serves users in multiple countries
• Response time is critical (user-facing features, real-time calculations)
• You want to avoid writing and maintaining date arithmetic logic
• You need batch processing for multiple dates

Choose a Holiday-Only API When:

• You only need raw holiday data, not business day math
• You want to build custom business day logic for a specific use case
• You need coverage for 100+ countries and do not mind building the calculation layer
• Your usage is minimal enough that a fully free tier matters more than features

Choose a General Date API When:

• You need holiday data as part of a broader date and time feature set
• Business day calculations are a secondary need, not a primary one
• You are already using a general-purpose API for other date operations

A Real-World Example

Consider a SaaS invoicing platform that needs to calculate payment due dates in business days for clients in the US, UK, and Germany. With a holiday-only API, you would:

1. Fetch holiday lists for each country and year
2. Cache them locally
3. Write a function that skips weekends and holidays
4. Handle country-specific weekend definitions
5. Test and maintain this code across edge cases

With BizDay, the same feature is a single API call:

// Invoice due in 30 business days for a UK client
const res = await fetch(
  'https://api.bizday.dev/v1/add?date=2026-03-09&days=30&country=GB',
  { headers: { Authorization: `Bearer ${API_KEY}` } }
);
const { data } = await res.json();
console.log(data.result_date); // "2026-04-22"
// Correctly skips UK bank holidays + weekends

Pricing Overview

Pricing varies significantly across services. BizDay starts at free (10,000 requests per month) with paid plans from $19/month for 100,000 requests. Holiday-only APIs range from completely free (with rate limits) to paid tiers that charge per request. General date APIs typically start at $10-50 per month.

The most important factor is not the raw price but the total cost of ownership. If a cheaper API requires you to build and maintain business day logic yourself, the engineering time may outweigh the savings on API costs.

Getting Started with BizDay

The free tier requires no credit card and takes seconds to set up. You can get your API key and start making requests immediately. Check the documentation for the full endpoint reference, code examples in multiple languages, and integration guides.