The takeaway
US Treasury 12 Month Bill ETF shows a slight seasonal lean over 4 years of data — strongest in December (+0.5%) and softest in February (+0.2%).
Right now
In July, the fund has risen 100% of years, averaging +0.4%, roughly 1.7 pts behind the S&P 500.
The full picture
US Treasury 12 Month Bill ETF's most dependable month has been December, higher in 4 of 4 years; February has been its least reliable, up just 100% of the time.
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Win rate % | ||||||||||||
| Median return % | ||||||||||||
| 2025 | ||||||||||||
| 2024 | ||||||||||||
| 2023 | ||||||||||||
| 2022 | — | — | — | — | — | — | — | — | — | — |
Month by month
The fund's clearest edge over the S&P 500 lands in September (+0.6 pts); it has trailed the market most in November (−2.0 pts).
“vs S&P” is US Treasury 12 Month Bill ETF’s average for a month minus the S&P 500’s average for that same month — isolating US Treasury 12 Month Bill ETF’s own seasonal edge from broad market drift.
Reality check
Over the last 4 years, December has closed higher 100% of the time versus 100% across the last 4 years — the pattern is holding.
Figures are the typical (median) December return and how often it rose — the last 4 years versus the last 4(the heatmap’s default window). This verdict stays anchored to that 4-year window even if you zoom the chart, so it never disagrees with the badges above.
In plain English
This is a fund you can almost set a calendar by, and December is the anchor — it has closed higher in all 4 Decembers, the steadiest beat on its year.
The strength looks broad-based rather than freakish: its average (+0.5%) and median (+0.5%) sit close together, so no single blow-out year is flattering the figure. Few months are steadier: December's returns vary by just 0.1% year to year, and even its worst December in 4 years lost only 0.4% — the gentlest downside anywhere on its calendar. Few peers keep such company in December — the typical stock clears it just 58% of the time.
The lift is near-universal — strength runs through almost every month of the year, not one window. On the other side of the ledger, February is the year's quietest corner, essentially flat on average, and the edge isn't year-round — the fund has trailed the S&P 500 in November, July, and April.
For a fund this dependable in December, the sharper question is the rest of the year — outside its strong stretch, the calendar gives far less to lean on. With a short 4-year record, the signal is best held loosely.
Short answers on the fund's best month (December), its worst (February), and whether it really trades seasonally.
Only mildly. The fund's months are fairly even — December is the firmest (+0.5%) and February the softest (+0.2%), a narrow spread that points to weak seasonality rather than a strong calendar effect.
December has been the strongest, averaging +0.5% and closing higher in all 4 years on record since 2022.
It's the weakest month, but it has still averaged a small gain (+0.2%) — quiet rather than genuinely bad.
Explore
These names have the strongest July track records on record — a starting point for comparison.
Before you trade