diff --git a/Cargo.lock b/Cargo.lock
index 2e9e648..90a5b1d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -122,9 +122,9 @@ checksum = "9330f8b2ff13f34540b44e946ef35111825727b38d33286ef986142615121801"
 
 [[package]]
 name = "chrono"
-version = "0.4.43"
+version = "0.4.44"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fac4744fb15ae8337dc853fee7fb3f4e48c0fbaa23d0afe49c447b4fab126118"
+checksum = "c673075a2e0e5f4a1dde27ce9dee1ea4558c7ffe648f576438a20ca1d2acc4b0"
 dependencies = [
  "iana-time-zone",
  "js-sys",
@@ -382,9 +382,9 @@ dependencies = [
 
 [[package]]
 name = "qtty"
-version = "0.3.0"
+version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ec18b86dcb4c777f979a171699a5f552675bbbfd7406d3d002403a26d7bd3215"
+checksum = "b42948ee9aba0ed2217fd0d89a666df2ab020e3e25ef9b0328150e6d6c0aaee3"
 dependencies = [
  "qtty-core",
  "qtty-derive",
@@ -392,9 +392,9 @@ dependencies = [
 
 [[package]]
 name = "qtty-core"
-version = "0.3.0"
+version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "02271e8e4889de336896d2b690ad40ef811e68a81726885a7ddfbccf7e35b19c"
+checksum = "283c549662e44f8a2848964e9639f2924f7a442f94294d508fc70c531a9717b3"
 dependencies = [
  "libm",
  "qtty-derive",
@@ -403,15 +403,29 @@ dependencies = [
 
 [[package]]
 name = "qtty-derive"
-version = "0.3.0"
+version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a6b1435ce1b31534c420c9b7c08dc7cf1d4a39f18748e7c7f29b71296d558a51"
+checksum = "5edb55d59461af47a984baae7fafc2374dac2a79d41434a77ee7807f0f592757"
 dependencies = [
  "proc-macro2",
  "quote",
  "syn",
 ]
 
+[[package]]
+name = "qtty-ffi"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d93de7d3db9abe1006b8a8b635de51f6d967636be144d06c28f66c3b8a49bd17"
+dependencies = [
+ "cbindgen",
+ "qtty",
+ "quote",
+ "serde",
+ "serde_json",
+ "syn",
+]
+
 [[package]]
 name = "quote"
 version = "1.0.44"
@@ -567,6 +581,7 @@ dependencies = [
  "cbindgen",
  "chrono",
  "qtty",
+ "qtty-ffi",
  "serde_json",
  "tempoch",
 ]
diff --git a/tempoch-core/Cargo.toml b/tempoch-core/Cargo.toml
index 83366ea..13dce94 100644
--- a/tempoch-core/Cargo.toml
+++ b/tempoch-core/Cargo.toml
@@ -17,7 +17,7 @@ path = "src/lib.rs"
 
 [dependencies]
 chrono = "0.4.43"
-qtty = "0.3.0"
+qtty = "0.3.1"
 serde = { version = "1.0", default-features = false, features = ["derive"], optional = true }
 
 [dev-dependencies]
diff --git a/tempoch-ffi/Cargo.toml b/tempoch-ffi/Cargo.toml
index 11abe86..d84e80a 100644
--- a/tempoch-ffi/Cargo.toml
+++ b/tempoch-ffi/Cargo.toml
@@ -17,8 +17,9 @@ serde = ["tempoch/serde", "dep:serde_json"]
 
 [dependencies]
 tempoch = { path = "../tempoch", version = "0.3.0" }
-qtty = "0.3.0"
-chrono = "0.4.43"
+qtty = "0.3.1"
+qtty-ffi = "0.3.1"
+chrono = "0.4.44"
 serde_json = { version = "1.0", optional = true }
 
 [build-dependencies]
diff --git a/tempoch-ffi/cbindgen.toml b/tempoch-ffi/cbindgen.toml
index 10247b1..42c6ed0 100644
--- a/tempoch-ffi/cbindgen.toml
+++ b/tempoch-ffi/cbindgen.toml
@@ -4,16 +4,23 @@ autogen_warning = "/* Warning: this file is auto-generated by cbindgen. Do not m
 documentation_style = "c99"
 style = "both"
 cpp_compat = true
+after_includes = """
+/* QttyQuantity and UnitId definitions come from qtty_ffi.h */
+#include "qtty_ffi.h"
+"""
 
 [defines]
 "feature = serde" = "TEMPOCH_FFI_HAS_SERDE"
 
 [export]
+# Exclude qtty-ffi types — they come from qtty_ffi.h (included via after_includes)
+exclude = ["QttyQuantity", "UnitId", "DimensionId", "QttyDerivedQuantity"]
 
 [export.rename]
 "TempochStatus" = "tempoch_status_t"
 "TempochUtc" = "tempoch_utc_t"
 "TempochPeriodMjd" = "tempoch_period_mjd_t"
+"QttyQuantity" = "qtty_quantity_t"
 
 [enum]
 rename_variants = "ScreamingSnakeCase"
diff --git a/tempoch-ffi/include/tempoch_ffi.h b/tempoch-ffi/include/tempoch_ffi.h
index c8a8674..db6e225 100644
--- a/tempoch-ffi/include/tempoch_ffi.h
+++ b/tempoch-ffi/include/tempoch_ffi.h
@@ -7,6 +7,9 @@
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdlib.h>
+/* QttyQuantity and UnitId definitions come from qtty_ffi.h */
+#include "qtty_ffi.h"
+
 
 // Status codes returned by tempoch-ffi functions.
 //
@@ -131,6 +134,32 @@ tempoch_status_t tempoch_period_mjd_intersection(struct tempoch_period_mjd_t a,
 // Compute Julian centuries since J2000 for a given Julian Date.
  double tempoch_jd_julian_centuries(double jd);
 
+// Compute the difference between two Julian Dates as a `QttyQuantity` in days.
+ qtty_quantity_t tempoch_jd_difference_qty(double jd1, double jd2);
+
+// Add a `QttyQuantity` duration (must be time-compatible) to a Julian Date.
+// The quantity is converted to days internally.
+//
+// # Safety
+// `out` must be a valid, writable pointer to `f64`.
+ tempoch_status_t tempoch_jd_add_qty(double jd, qtty_quantity_t duration, double *out);
+
+// Compute the difference between two Modified Julian Dates as a `QttyQuantity` in days.
+ qtty_quantity_t tempoch_mjd_difference_qty(double mjd1, double mjd2);
+
+// Add a `QttyQuantity` duration (must be time-compatible) to a Modified Julian Date.
+// The quantity is converted to days internally.
+//
+// # Safety
+// `out` must be a valid, writable pointer to `f64`.
+ tempoch_status_t tempoch_mjd_add_qty(double mjd, qtty_quantity_t duration, double *out);
+
+// Compute Julian centuries since J2000 as a `QttyQuantity`.
+ qtty_quantity_t tempoch_jd_julian_centuries_qty(double jd);
+
+// Compute the duration of a period as a `QttyQuantity` in days.
+ qtty_quantity_t tempoch_period_mjd_duration_qty(struct tempoch_period_mjd_t period);
+
 #ifdef __cplusplus
 }  // extern "C"
 #endif  // __cplusplus
diff --git a/tempoch-ffi/src/lib.rs b/tempoch-ffi/src/lib.rs
index e9b1460..b61e3d2 100644
--- a/tempoch-ffi/src/lib.rs
+++ b/tempoch-ffi/src/lib.rs
@@ -5,6 +5,9 @@
 //!
 //! This crate exposes a flat C-compatible API for creating and manipulating
 //! Julian Dates, Modified Julian Dates, time periods, and UTC conversions.
+//!
+//! Duration-related functions return [`QttyQuantity`] from qtty-ffi, providing
+//! type-safe unit information alongside numeric values.
 
 mod error;
 mod period;
@@ -14,6 +17,20 @@ pub use error::*;
 pub use period::*;
 pub use time::*;
 
+// Re-export qtty-ffi types used in our public FFI surface
+pub use qtty_ffi::{QttyQuantity, UnitId};
+
+/// Catches any panic and returns an error value instead of unwinding across FFI.
+macro_rules! catch_panic {
+    ($default:expr, $body:expr) => {{
+        match std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| $body)) {
+            Ok(result) => result,
+            Err(_) => $default,
+        }
+    }};
+}
+pub(crate) use catch_panic;
+
 /// Returns the tempoch-ffi ABI version (semver-encoded: major*10000 + minor*100 + patch).
 #[allow(clippy::erasing_op, clippy::identity_op)]
 #[no_mangle]
diff --git a/tempoch-ffi/src/period.rs b/tempoch-ffi/src/period.rs
index eb3a51f..1142985 100644
--- a/tempoch-ffi/src/period.rs
+++ b/tempoch-ffi/src/period.rs
@@ -3,6 +3,7 @@
 
 //! FFI bindings for tempoch period/interval types.
 
+use crate::catch_panic;
 use crate::error::TempochStatus;
 use tempoch::{Interval, ModifiedJulianDate, Period, MJD};
 
@@ -50,17 +51,18 @@ pub unsafe extern "C" fn tempoch_period_mjd_new(
     end_mjd: f64,
     out: *mut TempochPeriodMjd,
 ) -> TempochStatus {
-    if out.is_null() {
-        return TempochStatus::NullPointer;
-    }
-    if start_mjd > end_mjd {
-        return TempochStatus::InvalidPeriod;
-    }
-    // SAFETY: `out` was checked for null and the caller guarantees it points to writable memory.
-    unsafe {
-        *out = TempochPeriodMjd { start_mjd, end_mjd };
-    }
-    TempochStatus::Ok
+    catch_panic!(TempochStatus::InvalidPeriod, {
+        if out.is_null() {
+            return TempochStatus::NullPointer;
+        }
+        if start_mjd > end_mjd {
+            return TempochStatus::InvalidPeriod;
+        }
+        unsafe {
+            *out = TempochPeriodMjd { start_mjd, end_mjd };
+        }
+        TempochStatus::Ok
+    })
 }
 
 /// Compute the duration of a period in days.
@@ -80,17 +82,18 @@ pub unsafe extern "C" fn tempoch_period_mjd_intersection(
     b: TempochPeriodMjd,
     out: *mut TempochPeriodMjd,
 ) -> TempochStatus {
-    if out.is_null() {
-        return TempochStatus::NullPointer;
-    }
-    let pa = a.to_period();
-    let pb = b.to_period();
-    match pa.intersection(&pb) {
-        Some(result) => {
-            // SAFETY: `out` was checked for null and the caller guarantees it points to writable memory.
-            unsafe { *out = TempochPeriodMjd::from_period(&result) };
-            TempochStatus::Ok
+    catch_panic!(TempochStatus::NoIntersection, {
+        if out.is_null() {
+            return TempochStatus::NullPointer;
         }
-        None => TempochStatus::NoIntersection,
-    }
+        let pa = a.to_period();
+        let pb = b.to_period();
+        match pa.intersection(&pb) {
+            Some(result) => {
+                unsafe { *out = TempochPeriodMjd::from_period(&result) };
+                TempochStatus::Ok
+            }
+            None => TempochStatus::NoIntersection,
+        }
+    })
 }
diff --git a/tempoch-ffi/src/time.rs b/tempoch-ffi/src/time.rs
index e6e3929..4bdad8c 100644
--- a/tempoch-ffi/src/time.rs
+++ b/tempoch-ffi/src/time.rs
@@ -4,9 +4,11 @@
 //! FFI bindings for tempoch time types: JulianDate, ModifiedJulianDate,
 //! and UTC conversions.
 
+use crate::catch_panic;
 use crate::error::TempochStatus;
 use chrono::{DateTime, NaiveDate, Utc};
 use qtty::Days;
+use qtty_ffi::{QttyQuantity, UnitId};
 use tempoch::{JulianDate, ModifiedJulianDate, TimeInstant, JD, MJD};
 
 // ═══════════════════════════════════════════════════════════════════════════
@@ -80,18 +82,19 @@ pub extern "C" fn tempoch_jd_to_mjd(jd: f64) -> f64 {
 /// `out` must be a valid, writable pointer to `f64`.
 #[no_mangle]
 pub unsafe extern "C" fn tempoch_jd_from_utc(utc: TempochUtc, out: *mut f64) -> TempochStatus {
-    if out.is_null() {
-        return TempochStatus::NullPointer;
-    }
-    match utc.into_chrono() {
-        Some(dt) => {
-            let jd = JulianDate::from_utc(dt);
-            // SAFETY: `out` was checked for null and the caller guarantees writable memory.
-            unsafe { *out = jd.value() };
-            TempochStatus::Ok
+    catch_panic!(TempochStatus::UtcConversionFailed, {
+        if out.is_null() {
+            return TempochStatus::NullPointer;
         }
-        None => TempochStatus::UtcConversionFailed,
-    }
+        match utc.into_chrono() {
+            Some(dt) => {
+                let jd = JulianDate::from_utc(dt);
+                unsafe { *out = jd.value() };
+                TempochStatus::Ok
+            }
+            None => TempochStatus::UtcConversionFailed,
+        }
+    })
 }
 
 /// Convert a Julian Date to UTC. Returns Ok on success,
@@ -101,17 +104,18 @@ pub unsafe extern "C" fn tempoch_jd_from_utc(utc: TempochUtc, out: *mut f64) ->
 /// `out` must be a valid, writable pointer to `TempochUtc`.
 #[no_mangle]
 pub unsafe extern "C" fn tempoch_jd_to_utc(jd: f64, out: *mut TempochUtc) -> TempochStatus {
-    if out.is_null() {
-        return TempochStatus::NullPointer;
-    }
-    match JulianDate::new(jd).to_utc() {
-        Some(dt) => {
-            // SAFETY: `out` was checked for null and the caller guarantees writable memory.
-            unsafe { *out = TempochUtc::from_chrono(&dt) };
-            TempochStatus::Ok
+    catch_panic!(TempochStatus::UtcConversionFailed, {
+        if out.is_null() {
+            return TempochStatus::NullPointer;
         }
-        None => TempochStatus::UtcConversionFailed,
-    }
+        match JulianDate::new(jd).to_utc() {
+            Some(dt) => {
+                unsafe { *out = TempochUtc::from_chrono(&dt) };
+                TempochStatus::Ok
+            }
+            None => TempochStatus::UtcConversionFailed,
+        }
+    })
 }
 
 // ═══════════════════════════════════════════════════════════════════════════
@@ -136,18 +140,19 @@ pub extern "C" fn tempoch_mjd_to_jd(mjd: f64) -> f64 {
 /// `out` must be a valid, writable pointer to `f64`.
 #[no_mangle]
 pub unsafe extern "C" fn tempoch_mjd_from_utc(utc: TempochUtc, out: *mut f64) -> TempochStatus {
-    if out.is_null() {
-        return TempochStatus::NullPointer;
-    }
-    match utc.into_chrono() {
-        Some(dt) => {
-            let mjd = ModifiedJulianDate::from_utc(dt);
-            // SAFETY: `out` was checked for null and the caller guarantees writable memory.
-            unsafe { *out = mjd.value() };
-            TempochStatus::Ok
+    catch_panic!(TempochStatus::UtcConversionFailed, {
+        if out.is_null() {
+            return TempochStatus::NullPointer;
         }
-        None => TempochStatus::UtcConversionFailed,
-    }
+        match utc.into_chrono() {
+            Some(dt) => {
+                let mjd = ModifiedJulianDate::from_utc(dt);
+                unsafe { *out = mjd.value() };
+                TempochStatus::Ok
+            }
+            None => TempochStatus::UtcConversionFailed,
+        }
+    })
 }
 
 /// Convert a Modified Julian Date to UTC.
@@ -156,19 +161,24 @@ pub unsafe extern "C" fn tempoch_mjd_from_utc(utc: TempochUtc, out: *mut f64) ->
 /// `out` must be a valid, writable pointer to `TempochUtc`.
 #[no_mangle]
 pub unsafe extern "C" fn tempoch_mjd_to_utc(mjd: f64, out: *mut TempochUtc) -> TempochStatus {
-    if out.is_null() {
-        return TempochStatus::NullPointer;
-    }
-    match ModifiedJulianDate::new(mjd).to_utc() {
-        Some(dt) => {
-            // SAFETY: `out` was checked for null and the caller guarantees writable memory.
-            unsafe { *out = TempochUtc::from_chrono(&dt) };
-            TempochStatus::Ok
+    catch_panic!(TempochStatus::UtcConversionFailed, {
+        if out.is_null() {
+            return TempochStatus::NullPointer;
         }
-        None => TempochStatus::UtcConversionFailed,
-    }
+        match ModifiedJulianDate::new(mjd).to_utc() {
+            Some(dt) => {
+                unsafe { *out = TempochUtc::from_chrono(&dt) };
+                TempochStatus::Ok
+            }
+            None => TempochStatus::UtcConversionFailed,
+        }
+    })
 }
 
+// ═══════════════════════════════════════════════════════════════════════════
+// Duration / Difference (raw f64 — backward compatible)
+// ═══════════════════════════════════════════════════════════════════════════
+
 /// Compute the difference between two Julian Dates in days.
 #[no_mangle]
 pub extern "C" fn tempoch_jd_difference(jd1: f64, jd2: f64) -> f64 {
@@ -205,6 +215,98 @@ pub extern "C" fn tempoch_jd_julian_centuries(jd: f64) -> f64 {
     JulianDate::new(jd).julian_centuries().value()
 }
 
+// ═══════════════════════════════════════════════════════════════════════════
+// Duration / Difference (QttyQuantity — typed)
+// ═══════════════════════════════════════════════════════════════════════════
+// These functions return `QttyQuantity` values with proper unit metadata,
+// enabling type-safe conversions via the qtty-ffi API.
+
+/// Compute the difference between two Julian Dates as a `QttyQuantity` in days.
+#[no_mangle]
+pub extern "C" fn tempoch_jd_difference_qty(jd1: f64, jd2: f64) -> QttyQuantity {
+    let t1 = JulianDate::new(jd1);
+    let t2 = JulianDate::new(jd2);
+    QttyQuantity::new(t1.difference(&t2).value(), UnitId::Day)
+}
+
+/// Add a `QttyQuantity` duration (must be time-compatible) to a Julian Date.
+/// The quantity is converted to days internally.
+///
+/// # Safety
+/// `out` must be a valid, writable pointer to `f64`.
+#[no_mangle]
+pub unsafe extern "C" fn tempoch_jd_add_qty(
+    jd: f64,
+    duration: QttyQuantity,
+    out: *mut f64,
+) -> TempochStatus {
+    catch_panic!(TempochStatus::UtcConversionFailed, {
+        if out.is_null() {
+            return TempochStatus::NullPointer;
+        }
+        // Convert quantity to days via qtty-ffi registry
+        let days_val = match duration.convert_to(UnitId::Day) {
+            Some(q) => q.value,
+            None => return TempochStatus::UtcConversionFailed,
+        };
+        let result = JulianDate::new(jd)
+            .add_duration(Days::new(days_val))
+            .value();
+        unsafe { *out = result };
+        TempochStatus::Ok
+    })
+}
+
+/// Compute the difference between two Modified Julian Dates as a `QttyQuantity` in days.
+#[no_mangle]
+pub extern "C" fn tempoch_mjd_difference_qty(mjd1: f64, mjd2: f64) -> QttyQuantity {
+    let t1 = ModifiedJulianDate::new(mjd1);
+    let t2 = ModifiedJulianDate::new(mjd2);
+    QttyQuantity::new(t1.difference(&t2).value(), UnitId::Day)
+}
+
+/// Add a `QttyQuantity` duration (must be time-compatible) to a Modified Julian Date.
+/// The quantity is converted to days internally.
+///
+/// # Safety
+/// `out` must be a valid, writable pointer to `f64`.
+#[no_mangle]
+pub unsafe extern "C" fn tempoch_mjd_add_qty(
+    mjd: f64,
+    duration: QttyQuantity,
+    out: *mut f64,
+) -> TempochStatus {
+    catch_panic!(TempochStatus::UtcConversionFailed, {
+        if out.is_null() {
+            return TempochStatus::NullPointer;
+        }
+        let days_val = match duration.convert_to(UnitId::Day) {
+            Some(q) => q.value,
+            None => return TempochStatus::UtcConversionFailed,
+        };
+        let result = ModifiedJulianDate::new(mjd)
+            .add_duration(Days::new(days_val))
+            .value();
+        unsafe { *out = result };
+        TempochStatus::Ok
+    })
+}
+
+/// Compute Julian centuries since J2000 as a `QttyQuantity`.
+#[no_mangle]
+pub extern "C" fn tempoch_jd_julian_centuries_qty(jd: f64) -> QttyQuantity {
+    QttyQuantity::new(
+        JulianDate::new(jd).julian_centuries().value(),
+        UnitId::JulianCentury,
+    )
+}
+
+/// Compute the duration of a period as a `QttyQuantity` in days.
+#[no_mangle]
+pub extern "C" fn tempoch_period_mjd_duration_qty(period: crate::TempochPeriodMjd) -> QttyQuantity {
+    QttyQuantity::new(period.end_mjd - period.start_mjd, UnitId::Day)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/tempoch/Cargo.toml b/tempoch/Cargo.toml
index 347bbf3..026bf43 100644
--- a/tempoch/Cargo.toml
+++ b/tempoch/Cargo.toml
@@ -22,7 +22,7 @@ serde = ["tempoch-core/serde"]
 tempoch-core = { path = "../tempoch-core", version = "0.3.0" }
 
 [dev-dependencies]
-chrono = "0.4.43"
-qtty = "0.3.0"
+chrono = "0.4.44"
+qtty = "0.3.1"
 serde_json = "1.0"