OA Date Converter

About This Tool

The OA Date Converter provides precise, reversible mappings between OA (OLE Automation) date values and standard date formats used in modern data workflows. OA dates are stored as a floating-point number of days since 1899-12-30, with the fractional part encoding the time of day. This tool accepts a numeric OA value or an ISO 8601 date, and returns both human-readable ISO strings and Unix timestamps, depending on the direction. It is intended for developers integrating legacy systems, data engineers cleaning dates in ETL pipelines, and analysts validating cross-system datasets. The core value lies in deterministic conversions that preserve fractional days and avoid locale assumptions.

Conceptually, OA_to_ISO adds the OA value to the origin date to yield a calendar moment, then formats that moment in ISO 8601 and computes a Unix epoch value when requested. ISO_to_OA parses the input date-time and subtracts the origin, converting the difference to days with fractional precision. The approach is deterministic and independent of user locale, ensuring consistent results across environments. The tool also documents the edge-case behavior for pre-origin dates and extremely large or tiny fractions, enabling reliable pipeline behavior and traceability in data logs.

Unique differentiators include explicit handling of fractional days, robust input validation, and clear error signaling for invalid formats. It supports both directions in a single interface, enabling seamless integration into code, scripts, or API workflows. By providing both ISO 8601 and Unix epoch outputs, it supports common ingestion points in analytics platforms and dashboards. The tool emphasizes accuracy, reproducibility, and simplicity, avoiding UI jargon while focusing on the domain logic that underpins date interoperability.

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