ml4t-calendar-ops SKILL.md skillA
ml4t-calendar-ops from ml4t/skills is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add ml4t/skills/ml4t-calendar-ops@git:20260901.c415df0Pins git:20260901.c415df0 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- ml4t/skills
- Path
data/calendar-ops/SKILL.md- Versions recorded
- 2
- Latest version
- git:20260901.c415df0, committed Sep 1, 2026
- First version recorded
- May 28, 2026
- Size
- 4,659 bytes
- Repository stars
- 41
- License
- Apache-2.0
Trading calendar awareness for correct date alignment and rolling windows. Use when aligning data across markets or computing holiday-aware windows.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Calendar Operations
Using calendar days instead of trading days for a 20-day rolling window includes weekends and holidays, producing a window that covers 28 calendar days but only 20 observations - silently misaligning your features with your labels.
## The Problem
Markets are closed on weekends and holidays. A "20-day momentum" signal should use 20 trading days (~4 weeks), not 20 calendar days (~2.8 weeks). When you mix calendar-day math with trading-day data, rolling windows span wrong periods, cross-market joins misalign (NYSE is closed on Presidents Day but LSE is open), and date arithmetic produces gaps your model interprets as missing data. These errors are invisible until you compare strategy behavior across markets or time zones.
## The Pattern
### WRONG
```python
import polars as pl
from datetime import timedelta
# Calendar days for rolling window - includes weekends, holidays
df = df.with_columns(
momentum=pl.col("close") / pl.col("close").shift(20) - 1 # shift(20) = 20 rows
)
# If data has gaps (holidays), shift(20) is NOT 20 trading days - it skips over them unevenly
# Date arithmetic for label alignment
df = df.with_columns(
…Read the whole file at its exact version.
How to install
mdr add ml4t/skills/ml4t-calendar-ops@sha256:8e463698e1ccb41eThe line at the top of this page pins the label git:20260901.c415df0, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_xri2w3jywyryamyb)
2 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 2 versions of this file, between May 28, 2026 and Sep 1, 2026, about one every 96 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20260901.c415df0 latest | 2026-09-01 | c415df0 | 4,659 B | A | view · diff |
| git:20260528.303089e | 2026-05-28 | 303089e | 4,675 B | A | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (4659 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
ml4t/skills · 41 stars · license Apache-2.0 · pushed 2026-11-08 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_xri2w3jywyryamyb GET https://markdownregistry.com/api/v1/resolve?ref=ml4t/skills/ml4t-calendar-ops GET https://markdownregistry.com/api/v1/blob/8e463698e1ccb41edcac3e9164fac409efc3e6a8bd79222bdfc58b7b6cfb467f
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.