diff --git a/Cargo.lock b/Cargo.lock
index ecb34e8..c2082bb 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -131,7 +131,7 @@ checksum = "3b43422f69d8ff38f95f1b2bb76517c91589a924d1559a0e935d7c8ce0274c11"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -142,7 +142,7 @@ checksum = "644dd749086bf3771a2fbc5f256fdb982d53f011c7d5d560304eafeecebce79d"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -239,6 +239,12 @@ version = "0.14.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2d7e60934ceec538daadb9d8432424ed043a904d8e0243f3c6446bce549a46ac"
 
+[[package]]
+name = "bitflags"
+version = "1.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
+
 [[package]]
 name = "bitflags"
 version = "2.6.0"
@@ -385,7 +391,7 @@ dependencies = [
  "num-traits",
  "serde",
  "wasm-bindgen",
- "windows-link",
+ "windows-link 0.1.0",
 ]
 
 [[package]]
@@ -447,7 +453,7 @@ dependencies = [
  "heck",
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -608,7 +614,7 @@ checksum = "a851e4efac7afda4a5e1a11fea1d65ef528dbdcff08177d7087e4bb6225e60a9"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -632,7 +638,7 @@ dependencies = [
  "proc-macro2",
  "quote",
  "strsim",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -643,7 +649,38 @@ checksum = "d38308df82d1080de0afee5d069fa14b0326a88c14f15c5ccda35b4a6c414c81"
 dependencies = [
  "darling_core",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
+]
+
+[[package]]
+name = "defmt"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2953bfe4f93bbd20cc71198842756f77d161884c99ebbabc41d80231ded88d1"
+dependencies = [
+ "bitflags 1.3.2",
+ "defmt-macros",
+]
+
+[[package]]
+name = "defmt-macros"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bad9c72e7ca2137e0dc3813245a0d282fd6daad32fd800af018306a9169b5fe8"
+dependencies = [
+ "defmt-parser",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.119",
+]
+
+[[package]]
+name = "defmt-parser"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "10d60334b3b2e7c9d91ef8150abfb6fa4c1c39ebbcf4a81c2e346aad939fee3e"
+dependencies = [
+ "thiserror 2.0.12",
 ]
 
 [[package]]
@@ -667,7 +704,7 @@ checksum = "8034092389675178f570469e6c3b0465d3d30b4505c294a6550db47f3c17ad18"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -719,7 +756,7 @@ checksum = "97369cbbc041bc366949bc74d34658d6cda5621039731c6310521892a3a20ae0"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -901,7 +938,7 @@ checksum = "162ee34ebcb7c64a8abebc059ce0fee27c2262618d7b60ed8faf72fef13c3650"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -1210,7 +1247,7 @@ checksum = "1ec89e9337638ecdc08744df490b221a7399bf8d164eb52a665454e60e075ad6"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -1268,7 +1305,7 @@ version = "0.7.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fdd7bddefd0a8833b88a4b68f90dae22c7450d11b354198baee3874fd811b344"
 dependencies = [
- "bitflags",
+ "bitflags 2.6.0",
  "cfg-if",
  "libc",
 ]
@@ -1296,6 +1333,48 @@ version = "1.0.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "49f1f14873335454500d59611f1cf4a4b0f786f9ac11f4312a78e4cf2566695b"
 
+[[package]]
+name = "jiff"
+version = "0.2.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "961d16382652bfdd8c6f68b223b26a8c93e0d475c672f414411db31c6c5c900e"
+dependencies = [
+ "defmt",
+ "jiff-static",
+ "jiff-tzdb-platform",
+ "log",
+ "portable-atomic",
+ "portable-atomic-util",
+ "serde_core",
+ "windows-link 0.2.1",
+]
+
+[[package]]
+name = "jiff-static"
+version = "0.2.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d0879bd39df99c4c5e2c6615ccc026391a423dde10532c573e6086eb94a802cc"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.119",
+]
+
+[[package]]
+name = "jiff-tzdb"
+version = "0.1.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "142bd39932ad231f10513df9ab62661fead8719872150b7ad02a2df79f4e141e"
+
+[[package]]
+name = "jiff-tzdb-platform"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "875a5a69ac2bab1a891711cf5eccbec1ce0341ea805560dcd90b7a2e925132e8"
+dependencies = [
+ "jiff-tzdb",
+]
+
 [[package]]
 name = "jobserver"
 version = "0.1.32"
@@ -1341,7 +1420,7 @@ version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c0ff37bd590ca25063e35af745c343cb7a0271906fb7b37e4813e8f79f00268d"
 dependencies = [
- "bitflags",
+ "bitflags 2.6.0",
  "libc",
  "redox_syscall",
 ]
@@ -1531,8 +1610,7 @@ dependencies = [
 [[package]]
 name = "olpc-cjson"
 version = "0.1.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "696183c9b5fe81a7715d074fd632e8bd46f4ccc0231a3ed7fc580a80de5f7083"
+source = "git+https://github.com/oxidecomputer/tough?branch=oxide%2Fdevelop#56967c9651efcffd7326198f04fc388c4f0f92b9"
 dependencies = [
  "serde",
  "serde_json",
@@ -1621,7 +1699,7 @@ checksum = "a4502d8515ca9f32f1fb543d987f63d95a14934883db45bdb48060b6b69257f8"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -1663,6 +1741,21 @@ version = "0.3.31"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "953ec861398dccce10c670dfeaf3ec4911ca479e9c02154b3a215178c5f566f2"
 
+[[package]]
+name = "portable-atomic"
+version = "1.13.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c33a9471896f1c69cecef8d20cbe2f7accd12527ce60845ff44c153bb2a21b49"
+
+[[package]]
+name = "portable-atomic-util"
+version = "0.2.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c2a106d1259c23fac8e543272398ae0e3c0b8d33c88ed73d0cc71b0f1d902618"
+dependencies = [
+ "portable-atomic",
+]
+
 [[package]]
 name = "powerfmt"
 version = "0.2.0"
@@ -1695,7 +1788,7 @@ checksum = "b4c2511913b88df1637da85cc8d96ec8e43a3f8bb8ccb71ee1ac240d6f3df58d"
 dependencies = [
  "bit-set",
  "bit-vec",
- "bitflags",
+ "bitflags 2.6.0",
  "lazy_static",
  "num-traits",
  "rand",
@@ -1800,7 +1893,7 @@ version = "0.5.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9b6dfecf2c74bce2466cabf93f6664d6998a69eb21e39f4207930065b27b771f"
 dependencies = [
- "bitflags",
+ "bitflags 2.6.0",
 ]
 
 [[package]]
@@ -1820,7 +1913,7 @@ checksum = "b7186006dcb21920990093f30e3dea63b7d6e977bf1256be20c3563a5db070da"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -1873,7 +1966,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b91f7eff05f748767f183df4320a63d6936e9c6107d97c9e6bdd9784f4289c94"
 dependencies = [
  "base64 0.21.7",
- "bitflags",
+ "bitflags 2.6.0",
  "serde",
  "serde_derive",
 ]
@@ -1912,7 +2005,7 @@ version = "0.38.37"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8acb788b847c24f28525660c4d7758620a7210875711f79e7f663cc152726811"
 dependencies = [
- "bitflags",
+ "bitflags 2.6.0",
  "errno",
  "libc",
  "linux-raw-sys 0.4.14",
@@ -1925,7 +2018,7 @@ version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c71e83d6afe7ff64890ec6b71d6a69bb8a610ab78ce364b3352876bb4c801266"
 dependencies = [
- "bitflags",
+ "bitflags 2.6.0",
  "errno",
  "libc",
  "linux-raw-sys 0.9.4",
@@ -2046,7 +2139,7 @@ dependencies = [
  "proc-macro2",
  "quote",
  "serde_derive_internals",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -2096,7 +2189,7 @@ checksum = "d540f220d3187173da220f885ab66608367b6574e925011a9353e4badda91d79"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -2107,7 +2200,7 @@ checksum = "18d26a20a969b9e3fdf2fc2d9f21eda6c40e2de84c9408bb5d3b05d499aae711"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -2169,7 +2262,7 @@ dependencies = [
  "darling",
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -2329,7 +2422,7 @@ dependencies = [
  "heck",
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -2369,7 +2462,7 @@ dependencies = [
  "proc-macro2",
  "quote",
  "structmeta-derive",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -2380,7 +2473,7 @@ checksum = "152a0b65a590ff6c3da95cabe2353ee04e6167c896b28e3b14478c2636c922fc"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -2402,7 +2495,7 @@ dependencies = [
  "proc-macro2",
  "quote",
  "rustversion",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -2424,9 +2517,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "2.0.96"
+version = "2.0.119"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d5d0adab1ae378d7f53bdebc67a39f1f151407ef230f0ce2883572f5d8985c80"
+checksum = "872831b642d1a07999a962a351ed35b955ea2cfc8f3862091e2a240a84f17297"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -2441,7 +2534,7 @@ checksum = "c8af7666ab7b6390ab78131fb5b0fce11d6b7a6951602017c35fa82800708971"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -2517,7 +2610,7 @@ dependencies = [
  "proc-macro2",
  "quote",
  "structmeta",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -2546,7 +2639,7 @@ checksum = "4fee6c4efc90059e10f81e6d42c60a18f76588c3d74cb83a0b242a2b6c7504c1"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -2557,7 +2650,7 @@ checksum = "7f7cf42b4507d8ea322120659672cf1b9dbb93f8f2d4ecfd6e51350ff5b17a1d"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -2644,7 +2737,7 @@ checksum = "8d9ef545650e79f30233c0003bcc2504d7efac6dad25fca40744de773fe2049c"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -2692,7 +2785,7 @@ checksum = "6e06d43f1345a3bcd39f6a56dbb7dcab2ba47e68e8ac134855e7e2bdbaf8cab8"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -2766,20 +2859,19 @@ dependencies = [
 
 [[package]]
 name = "tough"
-version = "0.22.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8031cff0872dd1c6312370515a6be8098f6ea5512f1bad725016046fc725f272"
+version = "0.24.0"
+source = "git+https://github.com/oxidecomputer/tough?branch=oxide%2Fdevelop#56967c9651efcffd7326198f04fc388c4f0f92b9"
 dependencies = [
  "async-recursion",
  "async-trait",
  "aws-lc-rs",
  "bytes",
- "chrono",
  "dyn-clone",
  "futures",
  "futures-core",
  "globset",
  "hex",
+ "jiff",
  "log",
  "olpc-cjson",
  "pem",
@@ -2815,6 +2907,7 @@ dependencies = [
  "futures-util",
  "hex",
  "hubtools",
+ "jiff",
  "memchr",
  "rats-corim",
  "rawzip",
@@ -3029,7 +3122,7 @@ dependencies = [
  "once_cell",
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
  "wasm-bindgen-shared",
 ]
 
@@ -3051,7 +3144,7 @@ checksum = "26c6ab57572f7a24a4985830b120de1594465e5d500f24afe89e16b4e833ef68"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
  "wasm-bindgen-backend",
  "wasm-bindgen-shared",
 ]
@@ -3086,6 +3179,12 @@ version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6dccfd733ce2b1753b03b6d3c65edf020262ea35e20ccdf3e288043e6dd620e3"
 
+[[package]]
+name = "windows-link"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f0805222e57f7521d6a62e36fa9163bc891acd422f971defe97d64e70d0a4fe5"
+
 [[package]]
 name = "windows-sys"
 version = "0.52.0"
@@ -3183,7 +3282,7 @@ version = "0.39.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6f42320e61fe2cfd34354ecb597f86f413484a798ba44a8ca1165c58d42da6c1"
 dependencies = [
- "bitflags",
+ "bitflags 2.6.0",
 ]
 
 [[package]]
@@ -3250,7 +3349,7 @@ checksum = "28cc31741b18cb6f1d5ff12f5b7523e3d6eb0852bbbad19d73905511d9849b95"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
  "synstructure",
 ]
 
@@ -3291,7 +3390,7 @@ checksum = "125139de3f6b9d625c39e2efdd73d41bdac468ccd556556440e322be0e1bbd91"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -3302,7 +3401,7 @@ checksum = "fa4f8080344d4671fb4e831a13ad1e68092748387dfc4f55e356242fae12ce3e"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -3313,7 +3412,7 @@ checksum = "88d2b8d9c68ad2b9e4340d7832716a4d21a22a1154777ad56ea55c51a9cf3831"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -3333,7 +3432,7 @@ checksum = "0ea7b4a3637ea8669cedf0f1fd5c286a17f3de97b8dd5a70a6c167a1730e63a5"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
  "synstructure",
 ]
 
@@ -3354,7 +3453,7 @@ checksum = "ce36e65b0d2999d2aafac989fb249189a141aee1f53c612c1f37d72631959f69"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
@@ -3376,7 +3475,7 @@ checksum = "6eafa6dfb17584ea3e2bd6e76e0cc15ad7af12b09abdd1ca55961bed9b1063c6"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.96",
+ "syn 2.0.119",
 ]
 
 [[package]]
diff --git a/Cargo.toml b/Cargo.toml
index 7c1e0bc..948d5f0 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -32,6 +32,7 @@ flate2 = "1.0.35"
 futures-util = "0.3.31"
 hex = "0.4.3"
 hubtools = { git = "https://github.com/oxidecomputer/hubtools.git", rev = "2b1ef9b38d75563ea800baa3b17327eec17b1b7a" }
+jiff = "0.2.32"
 memchr = "2.7.4"
 proptest = "1.5.0"
 rats-corim = { git = "https://github.com/oxidecomputer/rats-corim.git", rev = "f0d5d5168d3d31487a56df32c676b0c6240bcc6b" }
@@ -51,7 +52,7 @@ test-strategy = "0.4.0"
 thiserror = "2.0.12"
 tokio = "1.47.0"
 tokio-test = "0.4.5"
-tough = "0.22.0"
+tough = { git = "https://github.com/oxidecomputer/tough", branch = "oxide/develop", version = "0.24.0" }
 tufaceous.path = "lib"
 tufaceous-artifact.path = "artifact"
 tufaceous-brand-metadata.path = "brand-metadata"
diff --git a/lib/Cargo.toml b/lib/Cargo.toml
index dc78a27..c27e33f 100644
--- a/lib/Cargo.toml
+++ b/lib/Cargo.toml
@@ -20,6 +20,7 @@ flate2.workspace = true
 futures-util.workspace = true
 hex.workspace = true
 hubtools.workspace = true
+jiff.workspace = true
 rats-corim.workspace = true
 rawzip.workspace = true
 semver.workspace = true
diff --git a/lib/src/edit/root.rs b/lib/src/edit/root.rs
index da35189..15da9f4 100644
--- a/lib/src/edit/root.rs
+++ b/lib/src/edit/root.rs
@@ -11,6 +11,7 @@ use chrono::DateTime;
 use chrono::Utc;
 use serde::Deserialize;
 use serde::Serialize;
+use tough::KeyIdFormat;
 use tough::editor::signed::SignedRole;
 use tough::key_source::KeySource;
 use tough::schema;
@@ -21,6 +22,7 @@ use tough::schema::Signed;
 
 use crate::error::Error;
 use crate::error::ErrorKind;
+use crate::util::chrono_to_jiff;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Root {
@@ -43,7 +45,7 @@ impl Root {
     pub fn verify_self_signed(&self) -> Result<(), Error> {
         self.inner
             .signed
-            .verify_role(&self.inner)
+            .verify_role(&self.inner, KeyIdFormat::Any)
             .map_err(ErrorKind::RoleVerify)?;
         Ok(())
     }
@@ -89,7 +91,7 @@ pub(crate) async fn generate_root(
         spec_version: "1.0.0".into(),
         consistent_snapshot: false,
         version: NonZero::<u64>::MIN,
-        expires,
+        expires: chrono_to_jiff(expires),
         keys: HashMap::new(),
         roles: HashMap::new(),
         _extra: HashMap::new(),
diff --git a/lib/src/edit/sign.rs b/lib/src/edit/sign.rs
index 9188312..33be3b2 100644
--- a/lib/src/edit/sign.rs
+++ b/lib/src/edit/sign.rs
@@ -37,6 +37,7 @@ use crate::edit::source::TargetSource;
 use crate::error::Error;
 use crate::error::ErrorKind;
 use crate::error::try_path;
+use crate::util::chrono_to_jiff;
 
 pub(crate) const DEFAULT_VALIDITY: Duration =
     Duration::from_secs(60 * 60 * 24 * 7 /* 1 week */);
@@ -162,11 +163,11 @@ impl<'a> UnsignedRepository<'a> {
             tough::editor::RepositoryEditor::new(&root_path).await?;
         editor
             .snapshot_version(self.snapshot_version)
-            .snapshot_expires(self.snapshot_expires)
+            .snapshot_expires(chrono_to_jiff(self.snapshot_expires))
             .targets_version(self.targets_version)?
-            .targets_expires(self.targets_expires)?
+            .targets_expires(chrono_to_jiff(self.targets_expires))?
             .timestamp_version(self.timestamp_version)
-            .timestamp_expires(self.timestamp_expires);
+            .timestamp_expires(chrono_to_jiff(self.timestamp_expires));
 
         let mut sources = BTreeMap::new();
         for (target_name, Target { length, sha256, source }) in self.targets {
diff --git a/lib/src/util.rs b/lib/src/util.rs
index 97a7146..62f4f94 100644
--- a/lib/src/util.rs
+++ b/lib/src/util.rs
@@ -11,8 +11,12 @@ use std::task::Poll;
 use camino::FromPathBufError;
 use camino::Utf8Path;
 use camino::Utf8PathBuf;
+use chrono::DateTime;
+use chrono::Timelike as _;
+use chrono::Utc;
 use flate2::read::GzDecoder;
 use futures_util::Stream;
+use jiff::Timestamp;
 use tufaceous_artifact::Artifact;
 use tufaceous_artifact::ArtifactHash;
 use tufaceous_artifact::InstallinatorArtifact;
@@ -131,3 +135,20 @@ pub(crate) fn error_chain(mut error: &dyn std::error::Error) -> String {
     }
     s
 }
+
+pub(crate) fn chrono_to_jiff(chrono: DateTime<Utc>) -> Timestamp {
+    Timestamp::new(
+        chrono.timestamp(),
+        // Timestamp::new is documented to error out if the date is out of the supported range (not
+        // a problem for us) or if the nanoseconds are lower than -999_999_999 or greater than
+        // 999_999_999. Chrono documents that in case of leap seconds nanosecond() will return a
+        // value from 1_000_000_000 to 1_999_999_999, so we clamp that (jiff doesn't support leap
+        // seconds anyway).
+        chrono
+            .nanosecond()
+            .max(999_999_999)
+            .try_into()
+            .expect("nanosecond should be clamped"),
+    )
+    .expect("couldn't convert timestamp")
+}