---
name: Yesterday
slug: yesterday
category: AI Engineering
description: "Yesterday resolves 'yesterday' to a concrete ISO date range relative to run time, returning inclusive civil dates and exact UTC instants. Use it before tasks scoped to yesterday, such as daily reports or change summaries."
github: "https://github.com/chaitanyagiri/munder-difflin/tree/main/resources/skills/yesterday"
language: TypeScript
stars: 2178
forks: 253
install: "npx degit https://github.com/chaitanyagiri/munder-difflin/tree/main/resources/skills/yesterday ~/.claude/skills/yesterday"
installs_to: ~/.claude/skills/yesterday
source_path: resources/skills/yesterday/SKILL.md
collection_size: 17
category_size: 2451
collection_url: "https://dirskills.com/collections/chaitanyagiri/munder-difflin"
added: 2026-08-19T07:25:46.319Z
last_synced: 2026-08-19T07:25:46.319Z
canonical_url: "https://dirskills.com/skills/yesterday"
---

# Yesterday

Yesterday resolves 'yesterday' to a concrete ISO date range relative to run time, returning inclusive civil dates and exact UTC instants. Use it before tasks scoped to yesterday, such as daily reports or change summaries.

**Install:**

```bash
npx degit https://github.com/chaitanyagiri/munder-difflin/tree/main/resources/skills/yesterday ~/.claude/skills/yesterday
```

## README

## /yesterday

Get the concrete date range for **yesterday** by running the bundled resolver:

```bash
node "$AGENT_DIR/.claude/skills/temporal/when.mjs" yesterday
```

It prints a human-readable line plus a JSON record:

- `start` / `end` — inclusive civil dates (`YYYY-MM-DD`) in your local timezone
- `startUtc` / `endExclusiveUtc` — the same window as a half-open `[start, end)`
  range of exact UTC instants, for timestamp-based queries
- `days`, `timezone`, `asOf` — the span, your timezone, and when this resolved

Use the returned dates as the time bounds for the task at hand. **Do not derive
dates by hand** — this resolver is the source of truth. For the full window list
or an arbitrary range (e.g. `last45days`, `last6months`), see the `/temporal` skill.