dateling 1.3.0

dateling provides a normalized formal language and grammar for handling relative time expressions. It includes a DSL (domain-specific language) to represent time anchors, offsets, and modifiers, along with a robust parser and resolver to evaluate these expressions into concrete dates. The name 'dateling' comes from combining 'date' and 'handling', reflecting its purpose of handling complex date computations

dateling

🕰 dateling — A Time Expression DSL and parser for deterministic date calculations.

dateling provides a normalized formal language (DSL) to represent and resolve date calculations using structured expressions.
Instead of parsing ambiguous natural language, it offers a precise syntax to express relative and absolute dates, compute date ranges, and perform robust date arithmetic.

The name dateling comes from combining date and handling.

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🚀 Why dateling?

Most existing packages like dateparser or parsedatetime try to interpret free-text natural language into dates.
In contrast, dateling takes a strict, declarative, and composable approach, offering:

• ✅ Predictable & reproducible date evaluation
• ✅ Fully composable date expressions
• ✅ Explicit syntax without ambiguity
• ✅ Ideal for any system requiring controlled time range calculations
• ✅ No natural language processing — purely deterministic time logic

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📅 DSL Syntax

The general expression format is:

{anchor [+/- offset] | [modifiers]}

Anchors:

• today (system reference date)
• YYYYMMDD (e.g. 20250101)
• YYYY-MM-DD (e.g. 2025-01-01)

Offsets:

• Days: +Nd, -Nd
• Months: +Nm, -Nm
• Years: +Ny, -Ny

Modifiers:

• year_start → resolves to start of year
• year_end → resolves to end of year
• year=nearest_year → use anchor year, fallback to previous year if resulting date is in the future
• year=YYYY → explicitly set year
• month=MM → override month
• day=DD → override day

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📊 Examples

DSL Expression	Meaning
{today}	today's date
{today -1d}	1 day before today
{today -1y | year_start}	start of year, 1 year ago
{2025-01-01 +30y | year_end}	year-end of 30 years after Jan 1, 2025
{today | year=nearest_year, month=03, day=10}	resolves to March 10 of anchor year (or previous year if future)
{year=2023, month=05, day=15}	absolute date

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🔬 Evaluation Example (Reference date: 2025-06-11)

DSL	Output
{today}	2025-06-11
{today -1d}	2025-06-10
{today -365d | year=nearest_year}	2024-06-11
{today -3y}	2022-06-11
{today | year_start}	2025-01-01
{today | year_end}	2025-12-31
{today -1y | year_start}	2024-01-01
{today -1y | year_end}	2024-12-31
{today | year=nearest_year, month=06, day=10}	2025-06-10
{today -1y | year=nearest_year, month=03, day=10}	2024-03-10
{today | year=2024, month=06, day=10}	2024-06-10
{year=2022, month=05, day=15}	2022-05-15
2025-01-01	2025-01-01
20250101	2025-01-01
{1000-01-01 +30y | year_end}	1030-12-31
{today -36m}	2022-06-11

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⚙ Usage

from dateling import DatelingResolver

resolver = DatelingResolver()
date = resolver.resolve("{today -1y | year_start}")
print(date)

You may also set a fixed reference date:

resolver = DatelingResolver(reference_date="2025-06-11")
date = resolver.resolve("{today -3y | year_end}")
print(date)

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📦 Installation

pip install dateling

(Once released to PyPI)

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🔧 Design Philosophy

• 🧮 Formal expression language for time calculation
• 🔎 Fully deterministic, reproducible, and testable
• 🏷 No AI or natural language guessing
• 📈 Applicable across scheduling, reporting, ETL, search systems, financial applications, etc.

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📄 License

MIT License

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🔗 Related Alternatives

Package	Approach	Difference from dateling
dateparser	Natural language parsing	No DSL, free-text interpretation
parsedatetime	Human language parsing	No formal syntax, heuristic parsing
textX	Generic DSL builder	Requires custom DSL grammar creation
dateling	DSL-based date expression language	Strict syntax for controlled date calculations

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🧭 dateling: When you want to write date calculations, not guess them.