Documentation Index
Fetch the complete documentation index at: https://mintlify.com/kepano/obsidian-skills/llms.txt
Use this file to discover all available pages before exploring further.
Formulas are computed properties defined in the formulas: section of a .base file. Each formula is a named expression that Obsidian evaluates for every note in the base. Once defined, a formula is referenced anywhere a property identifier is accepted — in order:, properties:, and summaries: — using the formula.name prefix. Formulas make it possible to derive new values (status icons, countdown timers, word estimates, formatted strings) without modifying the underlying notes.
Defining Formulas
Each entry in formulas: maps a name to an expression string. Names must be valid YAML keys (no spaces; use underscores). Expressions follow the same syntax as filter expressions and have access to all note properties, file metadata, and built-in functions.
formulas:
# Simple arithmetic
total: "price * quantity"
# Conditional logic
status_icon: 'if(done, "✅", "⏳")'
# String formatting
formatted_price: 'if(price, price.toFixed(2) + " dollars")'
# Date formatting
created: 'file.ctime.format("YYYY-MM-DD")'
# Calculate days since created (use .days for Duration)
days_old: '(now() - file.ctime).days'
# Calculate days until due date
days_until_due: 'if(due_date, (date(due_date) - today()).days, "")'
Using Formulas in Views
After defining a formula, reference it with the formula. prefix in order: and properties: blocks. The prefix tells Bases to look up the formula rather than a frontmatter property.
formulas:
days_until_due: 'if(due, (date(due) - today()).days, "")'
priority_label: 'if(priority == 1, "🔴 High", if(priority == 2, "🟡 Medium", "🟢 Low"))'
properties:
formula.days_until_due:
displayName: "Days Until Due"
formula.priority_label:
displayName: Priority
views:
- type: table
name: "Active Tasks"
order:
- file.name
- formula.priority_label
- formula.days_until_due
summaries:
formula.days_until_due: Average
Duration Type
Subtracting two dates does not return a number — it returns a Duration type. Calling number functions like .round(), .floor(), or .ceil() directly on a Duration will cause an error. You must access a numeric field on the Duration first, then apply number functions to that field.
now() - file.ctime or date(due) - today()), the result is a Duration object with the following fields:
| Field | Type | Description |
|---|
duration.days | Number | Total days in the duration |
duration.hours | Number | Total hours in the duration |
duration.minutes | Number | Total minutes in the duration |
duration.seconds | Number | Total seconds in the duration |
duration.milliseconds | Number | Total milliseconds in the duration |
formulas:
# ✅ Returns a number (days)
days_old: '(now() - file.ctime).days'
# ✅ Returns a number (hours), then rounds it
hours_old: '(now() - file.ctime).hours.round(0)'
# ✅ Rounded days
days_until: '(date(due_date) - today()).days.round(0)'
formulas:
# ❌ WRONG — Duration does not support .round() directly
bad_days: '(now() - file.ctime).round(0)'
# ❌ WRONG — Duration does not support division
bad_calc: '((date(due) - today()) / 86400000).round(0)'
Date Arithmetic
Formulas support adding and subtracting durations from dates using a string shorthand for duration units.
Duration unit abbreviations:
| Unit | Abbreviations |
|---|
| Years | y, year, years |
| Months | M, month, months |
| Weeks | w, week, weeks |
| Days | d, day, days |
| Hours | h, hour, hours |
| Minutes | m, minute, minutes |
| Seconds | s, second, seconds |
formulas:
# Add a duration to a date
tomorrow: 'now() + "1 day"'
next_week: 'today() + "7d"'
next_month: 'today() + "1M"'
# Subtract a duration from a date
yesterday: 'now() - "1 day"'
# Subtract two dates → returns Duration
age: 'now() - file.ctime'
# Extract numeric value from Duration
age_days: '(now() - file.ctime).days'
age_hours: '(now() - file.ctime).hours'
YAML Quoting Rules
Because formula expressions often contain double-quoted string literals, YAML quoting requires care. The general rule is:
- Use single quotes around formulas that contain double quotes:
'if(done, "Yes", "No")'
- Use double quotes for simple expressions with no inner quotes:
"price * quantity"
- Never nest double quotes inside double quotes without escaping
formulas:
# ✅ CORRECT — single quotes wrap the expression containing double quotes
label: 'if(done, "Yes", "No")'
# ✅ CORRECT — double quotes are fine when no inner quotes are needed
total: "price * quantity"
# ❌ WRONG — double quotes inside double quotes breaks YAML parsing
bad_label: "if(done, "Yes", "No")"
Common Formula Patterns
The following patterns cover the most frequent formula use cases.
Status icon from a property value:
formulas:
status_icon: 'if(status == "reading", "📖", if(status == "done", "✅", "📚"))'
formulas:
days_until_due: 'if(due_date, (date(due_date) - today()).days, "")'
formulas:
is_overdue: 'if(due_date, date(due_date) < today() && status != "done", false)'
formulas:
year_read: 'if(finished_date, date(finished_date).year, "")'
Common formula errors to avoid:
- Duration without field access —
(now() - file.ctime).round(0) will error. Use (now() - file.ctime).days.round(0) instead.
- Missing null checks —
(date(due_date) - today()).days will crash if due_date is empty on some notes. Guard with if(due_date, ..., "").
- Referencing undefined formulas — Every
formula.X used in order:, properties:, or summaries: must have a matching entry in the formulas: block. A missing definition fails silently.